diff --git a/test/unit_test/static/CMakeLists.txt b/test/unit_test/static/CMakeLists.txt
index 79e746b7..65688088 100644
--- a/test/unit_test/static/CMakeLists.txt
+++ b/test/unit_test/static/CMakeLists.txt
@@ -22,6 +22,7 @@
 
 add_library(unit_tests_static
     cgs_test.cpp
+    custom_rep_test.cpp
     custom_unit_test.cpp
     data_test.cpp
     dimension_op_test.cpp
diff --git a/test/unit_test/static/custom_rep_test.cpp b/test/unit_test/static/custom_rep_test.cpp
new file mode 100644
index 00000000..1909dcb6
--- /dev/null
+++ b/test/unit_test/static/custom_rep_test.cpp
@@ -0,0 +1,239 @@
+// The MIT License (MIT)
+//
+// Copyright (c) 2018 Mateusz Pusz
+//
+// Permission is hereby granted, free of charge, to any person obtaining a copy
+// of this software and associated documentation files (the "Software"), to deal
+// in the Software without restriction, including without limitation the rights
+// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+// copies of the Software, and to permit persons to whom the Software is
+// furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in all
+// copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+// SOFTWARE.
+
+#include "units/math.h"
+#include "units/physical/si/area.h"
+#include "units/physical/si/frequency.h"
+#include "units/physical/si/velocity.h"
+#include <chrono>
+#include <utility>
+
+using namespace units;
+
+namespace {
+
+template<typename T>
+struct arithmetic_ops {
+  // constexpr T& operator+=(T other) { value_ += other.value_; return *this; }
+  // constexpr T& operator-=(T other) { value_ -= other.value_; return *this; }
+  // constexpr T& operator*=(T other) { value_ *= other.value_; return *this; }
+  // constexpr T& operator/=(T other) { value_ /= other.value_; return *this; }
+
+  // [[nodiscard]] constexpr T operator-() const { return T(-value_); }
+
+  [[nodiscard]] friend constexpr T operator+(T lhs, T rhs) {
+    return T(lhs.value_ + rhs.value_);
+  }
+  [[nodiscard]] friend constexpr T operator-(T lhs, T rhs) {
+    return T(lhs.value_ - rhs.value_);
+  }
+  [[nodiscard]] friend constexpr T operator*(T lhs, T rhs) {
+    return T(lhs.value_ * rhs.value_);
+  }
+  [[nodiscard]] friend constexpr T operator/(T lhs, T rhs) {
+    return T(lhs.value_ / rhs.value_);
+  }
+
+  [[nodiscard]] friend constexpr bool operator==(T lhs, T rhs) { return lhs.value_ == rhs.value_; }
+  [[nodiscard]] friend constexpr bool operator!=(T lhs, T rhs) { return !(lhs == rhs); }
+  [[nodiscard]] friend constexpr bool operator<(T lhs, T rhs) { return lhs.value_ < rhs.value_; }
+  [[nodiscard]] friend constexpr bool operator>(T lhs, T rhs) { return rhs < lhs; }
+  [[nodiscard]] friend constexpr bool operator<=(T lhs, T rhs) { return !(rhs < lhs); }
+  [[nodiscard]] friend constexpr bool operator>=(T lhs, T rhs) { return !(lhs < rhs); }
+};
+
+template<typename T>
+struct impl_constructible_impl_convertible : arithmetic_ops<impl_constructible_impl_convertible<T>> {
+  T value_{};
+  impl_constructible_impl_convertible() = default;
+  constexpr impl_constructible_impl_convertible(T v) : value_(std::move(v)) {}
+  constexpr operator const T&() const& { return value_; }
+};
+
+template<typename T>
+using impl_impl = impl_constructible_impl_convertible<T>;
+
+static_assert(std::convertible_to<float, impl_impl<float>>);
+static_assert(std::convertible_to<impl_impl<float>, float>);
+static_assert(units::Scalar<impl_impl<float>>);
+
+template<typename T>
+struct expl_constructible_impl_convertible : arithmetic_ops<expl_constructible_impl_convertible<T>> {
+  T value_{};
+  expl_constructible_impl_convertible() = default;
+  constexpr explicit expl_constructible_impl_convertible(T v) : value_(std::move(v)) {}
+  constexpr operator const T&() const& { return value_; }
+};
+
+template<typename T>
+using expl_impl = expl_constructible_impl_convertible<T>;
+
+static_assert(!std::convertible_to<float, expl_impl<float>>);
+static_assert(std::convertible_to<expl_impl<float>, float>);
+static_assert(units::Scalar<expl_impl<float>>);
+
+template<typename T>
+struct impl_constructible_expl_convertible : arithmetic_ops<impl_constructible_expl_convertible<T>> {
+  T value_{};
+  impl_constructible_expl_convertible() = default;
+  constexpr impl_constructible_expl_convertible(T v) : value_(std::move(v)) {}
+  constexpr explicit operator const T&() const& { return value_; }
+};
+
+template<typename T>
+using impl_expl = impl_constructible_expl_convertible<T>;
+
+static_assert(std::convertible_to<float, impl_expl<float>>);
+static_assert(!std::convertible_to<impl_expl<float>, float>);
+static_assert(units::Scalar<impl_expl<float>>);
+
+template<typename T>
+struct expl_constructible_expl_convertible : arithmetic_ops<expl_constructible_expl_convertible<T>> {
+  T value_{};
+  expl_constructible_expl_convertible() = default;
+  constexpr explicit expl_constructible_expl_convertible(T v) : value_(std::move(v)) {}
+  constexpr explicit operator const T&() const& { return value_; }
+};
+
+template<typename T>
+using expl_expl = expl_constructible_expl_convertible<T>;
+
+static_assert(!std::convertible_to<float, expl_expl<float>>);
+static_assert(!std::convertible_to<expl_expl<float>, float>);
+static_assert(units::Scalar<expl_expl<float>>);
+
+}  // namespace
+
+namespace units {
+
+template<typename T>
+inline constexpr bool treat_as_floating_point<impl_impl<T>> = std::is_floating_point_v<T>;
+
+template<typename T>
+inline constexpr bool treat_as_floating_point<expl_impl<T>> = std::is_floating_point_v<T>;
+
+template<typename T>
+inline constexpr bool treat_as_floating_point<impl_expl<T>> = std::is_floating_point_v<T>;
+
+template<typename T>
+inline constexpr bool treat_as_floating_point<expl_expl<T>> = std::is_floating_point_v<T>;
+
+template<typename T>
+struct quantity_values<impl_impl<T>> {
+  static constexpr impl_impl<T> zero() { return impl_impl<T>(0); }
+  static constexpr impl_impl<T> max() { return std::numeric_limits<T>::max(); }
+  static constexpr impl_impl<T> min() { return std::numeric_limits<T>::lowest(); }
+};
+
+}  // namespace units
+
+namespace std {
+
+// template<typename T, typename U>
+// struct common_type<my_value<T>, my_value<U>> : std::type_identity<my_value<common_type_t<T, U>>> {};
+
+// template<typename T, typename U>
+// struct common_type<my_value<T>, U> : common_type<T, U> {};
+
+// template<typename T, typename U>
+// struct common_type<T, my_value<U>> : common_type<T, U> {};
+
+}  // namespace std
+
+namespace {
+
+using namespace units::si;
+
+// constructors
+
+// Quantity from Scalar
+// int <- int
+static_assert(length<metre, int>(expl_impl<int>(1)).count() == 1);
+// static_assert(length<metre, int>(impl_expl<int>(1)).count() == 1);  // should not compile (not convertible)
+static_assert(length<metre, int>(int(impl_expl<int>(1))).count() == 1);
+// static_assert(length<metre, expl_impl<int>>(1).count() == expl_impl<int>{1});  // should not compile (not convertible)
+static_assert(length<metre, expl_impl<int>>(expl_impl<int>(1)).count() == expl_impl<int>{1});
+static_assert(length<metre, impl_expl<int>>(1).count() == impl_expl<int>{1});
+
+// double <- double
+static_assert(length<metre, double>(expl_impl<double>(1.0)).count() == 1.0);
+// static_assert(length<metre, double>(impl_expl<double>(1.0)).count() == 1.0);  // should not compile (not convertible)
+static_assert(length<metre, double>(double(impl_expl<double>(1.0))).count() == 1.0);
+// static_assert(length<metre, expl_impl<double>>(1.0).count() == expl_impl<double>{1.0});  // should not compile (not convertible)
+static_assert(length<metre, expl_impl<double>>(expl_impl<double>(1.0)).count() == expl_impl<double>{1.0});
+static_assert(length<metre, impl_expl<double>>(1.0).count() == impl_expl<double>{1.0});
+
+// double <- int
+static_assert(length<metre, double>(expl_impl<int>(1)).count() == 1.0);
+// static_assert(length<metre, double>(impl_expl<int>(1)).count() == 1.0);  // should not compile (not convertible)
+static_assert(length<metre, double>(int(impl_expl<int>(1))).count() == 1.0);
+// static_assert(length<metre, expl_impl<double>>(1).count() == expl_impl<double>{1});  // should not compile (not convertible)
+static_assert(length<metre, expl_impl<double>>(expl_impl<double>(1)).count() == expl_impl<double>{1});
+static_assert(length<metre, impl_expl<double>>(1).count() == impl_expl<double>{1.0});
+
+// int <- double
+// static_assert(length<metre, int>(expl_impl<double>(1.0)).count() == 1); // should not compile (truncating conversion)
+// static_assert(length<metre, impl_expl<int>>(1.0).count() == impl_expl<int>{1});   // should not compile (truncating conversion)
+
+// Quantity from other Quantity with different Rep
+// int <- int
+static_assert(length<metre, int>(length<metre, expl_impl<int>>(expl_impl<int>(1))).count() == 1);
+// static_assert(length<metre, int>(length<metre, impl_expl<int>>(1)).count() == 1);  // should not compile (not convertible)
+static_assert(length<metre, int>(quantity_cast<int>(length<metre, impl_expl<int>>(1))).count() == 1);
+// static_assert(length<metre, expl_impl<int>>(length<metre, int>(1)).count() == expl_impl<int>{1});  // should not compile (not convertible)
+static_assert(length<metre, expl_impl<int>>(quantity_cast<expl_impl<int>>(length<metre, int>(1))).count() == expl_impl<int>{1});
+static_assert(length<metre, impl_expl<int>>(length<metre, int>(1)).count() == impl_expl<int>{1});
+
+// double <- double
+static_assert(length<metre, double>(length<metre, expl_impl<double>>(expl_impl<double>(1.0))).count() == 1.0);
+// static_assert(length<metre, double>(length<metre, impl_expl<double>>(1.0)).count() == 1.0);  // should not compile (not convertible)
+static_assert(length<metre, double>(quantity_cast<double>(length<metre, impl_expl<double>>(1.0))).count() == 1.0);
+// static_assert(length<metre, expl_impl<double>>(length<metre>(1.0).count() == expl_impl<double>{1.0});  // should not compile (not convertible)
+static_assert(length<metre, expl_impl<double>>(quantity_cast<expl_impl<double>>(length<metre>(1.0))).count() == expl_impl<double>{1.0});
+static_assert(length<metre, impl_expl<double>>(length<metre>(1.0)).count() == impl_expl<double>{1.0});
+
+// double <- int
+static_assert(length<metre, double>(length<metre, expl_impl<int>>(expl_impl<int>(1))).count() == 1.0);
+// static_assert(length<metre, double>(length<metre, impl_expl<int>>(1)).count() == 1.0);  // should not compile (not convertible)
+static_assert(length<metre, double>(quantity_cast<int>(length<metre, impl_expl<int>>(1))).count() == 1.0);
+// static_assert(length<metre, expl_impl<double>>(length<metre, int>(1)).count() == expl_impl<double>{1});  // should not compile (not convertible)
+static_assert(length<metre, expl_impl<double>>(quantity_cast<expl_impl<double>>(length<metre, int>(1))).count() == expl_impl<double>{1});
+static_assert(length<metre, impl_expl<double>>(length<metre, int>(1)).count() == impl_expl<double>{1.0});
+
+// int <- double
+// static_assert(length<metre, int>(length<metre, expl_impl<double>>(1.0)).count() == 1); // should not compile (truncating conversion)
+// static_assert(length<metre, impl_expl<int>>(length<metre, double>(1.0)).count() == impl_expl<int>{1});   // should not compile (truncating conversion)
+
+// unit conversions
+
+static_assert(length<metre, impl_expl<int>>(length<kilometre, impl_expl<int>>(1)).count() == impl_expl<int>(1000));
+// static_assert(length<kilometre, impl_expl<int>>(length<metre, impl_expl<int>>(2000)).count() == impl_expl<int>(2));  // should not compile (truncating conversion)
+static_assert(length<kilometre, impl_expl<int>>(quantity_cast<kilometre>(length<metre, impl_expl<int>>(2000))).count() == impl_expl<int>(2));
+
+static_assert(length<metre, impl_impl<int>>::zero().count() == impl_impl<int>{0});
+static_assert(length<metre, impl_impl<int>>::min().count() == impl_impl<int>{std::numeric_limits<int>::lowest()});
+static_assert(length<metre, impl_impl<int>>::max().count() == impl_impl<int>{std::numeric_limits<int>::max()});
+static_assert(length<metre, impl_impl<double>>::zero().count() == impl_impl<double>{0.0});
+static_assert(length<metre, impl_impl<double>>::min().count() == impl_impl<double>{std::numeric_limits<double>::lowest()});
+static_assert(length<metre, impl_impl<double>>::max().count() == impl_impl<double>{std::numeric_limits<double>::max()});
+
+}  // namespace
diff --git a/test/unit_test/static/quantity_test.cpp b/test/unit_test/static/quantity_test.cpp
index da2f6d8a..b74e72ed 100644
--- a/test/unit_test/static/quantity_test.cpp
+++ b/test/unit_test/static/quantity_test.cpp
@@ -27,83 +27,8 @@
 #include <chrono>
 #include <utility>
 
-using namespace units;
-
 namespace {
 
-template<typename T>
-class my_value {
-  T value_{};
-
-public:
-  my_value() = default;
-  constexpr my_value(T v) : value_(std::move(v)) {}
-
-  // constexpr my_value& operator+=(my_value other) { value_ += other.value_; return *this; }
-  // constexpr my_value& operator-=(my_value other) { value_ -= other.value_; return *this; }
-  // constexpr my_value& operator*=(my_value other) { value_ *= other.value_; return *this; }
-  // constexpr my_value& operator/=(my_value other) { value_ /= other.value_; return *this; }
-
-  [[nodiscard]] constexpr my_value operator-() const { return my_value(-value_); }
-
-  [[nodiscard]] friend constexpr my_value operator+(my_value lhs, my_value rhs) {
-    return my_value(lhs.value_ + rhs.value_);
-  }
-  [[nodiscard]] friend constexpr my_value operator-(my_value lhs, my_value rhs) {
-    return my_value(lhs.value_ - rhs.value_);
-  }
-  [[nodiscard]] friend constexpr my_value operator*(my_value lhs, my_value rhs) {
-    return my_value(lhs.value_ * rhs.value_);
-  }
-  [[nodiscard]] friend constexpr my_value operator/(my_value lhs, my_value rhs) {
-    return my_value(lhs.value_ / rhs.value_);
-  }
-
-  [[nodiscard]] friend constexpr bool operator==(my_value lhs, my_value rhs) { return lhs.value_ == rhs.value_; }
-  [[nodiscard]] friend constexpr bool operator!=(my_value lhs, my_value rhs) { return !(lhs == rhs); }
-  [[nodiscard]] friend constexpr bool operator<(my_value lhs, my_value rhs) { return lhs.value_ < rhs.value_; }
-  [[nodiscard]] friend constexpr bool operator>(my_value lhs, my_value rhs) { return rhs < lhs; }
-  [[nodiscard]] friend constexpr bool operator<=(my_value lhs, my_value rhs) { return !(rhs < lhs); }
-  [[nodiscard]] friend constexpr bool operator>=(my_value lhs, my_value rhs) { return !(lhs < rhs); }
-
-  constexpr operator const T&() const& { return value_; }
-};
-
-}  // namespace
-
-namespace units {
-
-template<typename T>
-inline constexpr bool treat_as_floating_point<my_value<T>> = std::is_floating_point_v<T>;
-
-template<typename T>
-struct quantity_values<my_value<T>> {
-  static constexpr my_value<T> zero() { return my_value<T>(0); }
-  static constexpr my_value<T> max() { return std::numeric_limits<T>::max(); }
-  static constexpr my_value<T> min() { return std::numeric_limits<T>::lowest(); }
-};
-
-}  // namespace units
-
-namespace std {
-
-template<typename T, typename U>
-struct common_type<my_value<T>, my_value<U>> : std::type_identity<my_value<common_type_t<T, U>>> {};
-
-template<typename T, typename U>
-struct common_type<my_value<T>, U> : common_type<T, U> {};
-
-template<typename T, typename U>
-struct common_type<T, my_value<U>> : common_type<T, U> {};
-
-}  // namespace std
-
-namespace {
-
-static_assert(units::Scalar<my_value<float>>);
-static_assert(std::convertible_to<my_value<float>, float>);
-static_assert(std::convertible_to<float, my_value<float>>);
-
 using namespace units;
 using namespace units::si;
 
@@ -123,44 +48,24 @@ static_assert(std::is_same_v<length<kilometre, int>::unit, kilometre>);
 
 // constructors
 
-using my_int = my_value<int>;
-using my_double = my_value<double>;
-
 static_assert(length<metre, int>().count() == 0);
 constexpr length<metre, int> km{1000};
 static_assert(km.count() == 1000);
 static_assert(length<metre, int>(km).count() == km.count());
 
 static_assert(length<metre, int>(1).count() == 1);
-static_assert(length<metre, int>(my_value(1)).count() == 1);
-static_assert(length<metre, my_int>(1).count() == my_int{1});
 // static_assert(length<metre, int>(1.0).count() == 1);   // should not compile (truncating conversion)
-// static_assert(length<metre, int>(my_value(1.0)).count() == 1); // should not compile (truncating conversion)
-// static_assert(length<metre, my_int>(1.0).count() == my_int{1});   // should not compile (truncating conversion)
 static_assert(length<metre, double>(1.0).count() == 1.0);
-static_assert(length<metre, double>(my_value(1.0)).count() == 1.0);
 static_assert(length<metre, double>(1).count() == 1.0);
-static_assert(length<metre, double>(my_value(1)).count() == 1.0);
 static_assert(length<metre, double>(3.14).count() == 3.14);
-static_assert(length<metre, my_double>(1.0).count() == my_double{1.0});
-static_assert(length<metre, my_double>(1).count() == my_double{1.0});
-static_assert(length<metre, my_double>(3.14).count() == my_double{3.14});
 
 static_assert(length<metre, int>(km).count() == 1000);
 // static_assert(length<metre, int>(length<metre, double>(3.14)).count() == 3);   // should not compile (truncating conversion)
-static_assert(length<metre, int>(quantity_cast<length<metre, my_int>>(3.14q_m)).count() == 3);
-// static_assert(length<metre, int>(length<metre, my_double>(1000.0)).count() == 1000);   // should not compile (truncating conversion)
-// static_assert(length<metre, my_int>(1000.0q_m).count() == my_int{1000});   // should not compile (truncating conversion)
 static_assert(length<metre, double>(1000.0q_m).count() == 1000.0);
-static_assert(length<metre, double>(length<metre, my_double>(1000.0)).count() == 1000.0);
-static_assert(length<metre, my_double>(1000.0q_m).count() == my_double{1000.0});
 static_assert(length<metre, double>(km).count() == 1000.0);
-static_assert(length<metre, my_double>(km).count() == my_double{1000.0});
 static_assert(length<metre, int>(1q_km).count() == 1000);
 // static_assert(length<metre, int>(1q_s).count() == 1);   // should not compile (different dimensions)
 //static_assert(length<kilometre, int>(1010q_m).count() == 1);   // should not compile (truncating conversion)
-static_assert(length<kilometre, int>(quantity_cast<length<kilometre, my_int>>(1010q_m)).count() == 1);
-static_assert(length<metre, int>(quantity_cast<length<kilometre, my_int>>(1010q_m)).count() == 1000);
 
 // assignment operator
 
@@ -174,12 +79,6 @@ static_assert(length<metre, int>::max().count() == std::numeric_limits<int>::max
 static_assert(length<metre, double>::zero().count() == 0.0);
 static_assert(length<metre, double>::min().count() == std::numeric_limits<double>::lowest());
 static_assert(length<metre, double>::max().count() == std::numeric_limits<double>::max());
-static_assert(length<metre, my_int>::zero().count() == my_int{0});
-static_assert(length<metre, my_int>::min().count() == my_int{std::numeric_limits<int>::lowest()});
-static_assert(length<metre, my_int>::max().count() == my_int{std::numeric_limits<int>::max()});
-static_assert(length<metre, my_double>::zero().count() == my_double{0.0});
-static_assert(length<metre, my_double>::min().count() == my_double{std::numeric_limits<double>::lowest()});
-static_assert(length<metre, my_double>::max().count() == my_double{std::numeric_limits<double>::max()});
 
 // unary member operators