diff --git a/bench/bench_set.cpp b/bench/bench_set.cpp
index 5742f3b..5262760 100644
--- a/bench/bench_set.cpp
+++ b/bench/bench_set.cpp
@@ -229,6 +229,27 @@ cpu_times insert_time(vector<typename C::value_type> &unique_range, vector<typen
    return total_time.elapsed();
 }
 
+template<typename Iterator>
+bool check_not_end(vector<Iterator> &iterators, Iterator itend, std::size_t number_of_ends = 0)
+{
+   std::size_t end_count = 0;
+   for(std::size_t i = 0, max = iterators.size(); i != max; ++i){
+      if(iterators[i] == itend && (++end_count > number_of_ends) )
+         return false;
+   }
+   return true;
+}
+
+template<typename Iterator>
+bool check_all_not_empty(vector< std::pair<Iterator, Iterator > > &iterator_pairs)
+{
+   for(std::size_t i = 0, max = iterator_pairs.size(); i != max; ++i){
+      if(iterator_pairs[i].first == iterator_pairs[i].second)
+         return false;
+   }
+   return true;
+}
+
 template<typename C>
 cpu_times search_time(vector<typename C::value_type> &unique_range, const char *RangeType)
 {
@@ -239,72 +260,68 @@ cpu_times search_time(vector<typename C::value_type> &unique_range, const char *
    cpu_timer total_time;
    total_time.resume();
 
+   vector<typename C::iterator> v_it(N);
+   vector< std::pair<typename C::iterator, typename C::iterator> > v_itp(N);
+
    for(std::size_t i = 0; i != N; ++i){
       //Find
       {
-         std::size_t found = 0;
          find_timer.resume();
          for(std::size_t rep = 0; rep != 2; ++rep)
          for(std::size_t i = 0, max = unique_range.size(); i != max; ++i){
-            found += static_cast<std::size_t>(c.end() != c.find(unique_range[i]));
+            v_it[i] = c.find(unique_range[i]);
          }
          find_timer.stop();
-         if(found/2 != c.size()){
+         if(!check_not_end(v_it, c.end())){
             std::cout << "ERROR! find all elements not found" << std::endl;
          }
       }
       //Lower
       {
-         std::size_t found = 0;
          lower_timer.resume();
          for(std::size_t rep = 0; rep != 2; ++rep)
          for(std::size_t i = 0, max = unique_range.size(); i != max; ++i){
-            found += static_cast<std::size_t>(c.end() != c.lower_bound(unique_range[i]));
+            v_it[i] = c.lower_bound(unique_range[i]);
          }
          lower_timer.stop();
-         if(found/2 != c.size()){
+         if(!check_not_end(v_it, c.end())){
             std::cout << "ERROR! lower_bound all elements not found" << std::endl;
          }
       }
       //Upper
       {
-         std::size_t found = 0;
          upper_timer.resume();
          for(std::size_t rep = 0; rep != 2; ++rep)
          for(std::size_t i = 0, max = unique_range.size(); i != max; ++i){
-            found += static_cast<std::size_t>(c.end() != c.upper_bound(unique_range[i]));
+            v_it[i] = c.upper_bound(unique_range[i]);
          }
          upper_timer.stop();
-         if(found/2 != (c.size()-1)){
+         if(!check_not_end(v_it, c.end(), 1u)){
             std::cout << "ERROR! upper_bound all elements not found" << std::endl;
          }
       }
       //Equal
       {
-         std::size_t found = 0;
-         std::pair<typename C::iterator,typename C::iterator> ret;
          equal_range_timer.resume();
          for(std::size_t rep = 0; rep != 2; ++rep)
          for(std::size_t i = 0, max = unique_range.size(); i != max; ++i){
-            ret = c.equal_range(unique_range[i]);
-            found += static_cast<std::size_t>(ret.first != ret.second);
+            v_itp[i] = c.equal_range(unique_range[i]);
          }
          equal_range_timer.stop();
-         if(found/2 != c.size()){
+         if(!check_all_not_empty(v_itp)){
             std::cout << "ERROR! equal_range all elements not found" << std::endl;
          }
       }
       //Count
       {
-         std::size_t found = 0;
-         std::pair<typename C::iterator,typename C::iterator> ret;
+         std::size_t count = 0;
          count_timer.resume();
          for(std::size_t rep = 0; rep != 2; ++rep)
          for(std::size_t i = 0, max = unique_range.size(); i != max; ++i){
-            found += static_cast<std::size_t>(c.count(unique_range[i]));
+            count += c.count(unique_range[i]);
          }
          count_timer.stop();
-         if(found/2 != c.size()){
+         if(count/2 != c.size()){
             std::cout << "ERROR! count all elements not found" << std::endl;
          }
       }
diff --git a/include/boost/container/detail/flat_tree.hpp b/include/boost/container/detail/flat_tree.hpp
index 2d7634f..d3f9ee6 100644
--- a/include/boost/container/detail/flat_tree.hpp
+++ b/include/boost/container/detail/flat_tree.hpp
@@ -743,6 +743,12 @@ class flat_tree
    std::pair<const_iterator, const_iterator> equal_range(const key_type& k) const
    {  return this->priv_equal_range(this->cbegin(), this->cend(), k);  }
 
+   std::pair<iterator, iterator> lower_bound_range(const key_type& k)
+   {  return this->priv_lower_bound_range(this->begin(), this->end(), k);  }
+
+   std::pair<const_iterator, const_iterator> lower_bound_range(const key_type& k) const
+   {  return this->priv_lower_bound_range(this->cbegin(), this->cend(), k);  }
+
    size_type capacity() const          
    { return this->m_data.m_vect.capacity(); }
 
@@ -958,6 +964,18 @@ class flat_tree
       return std::pair<RanIt, RanIt>(first, first);
    }
 
+   template<class RanIt>
+   std::pair<RanIt, RanIt> priv_lower_bound_range(RanIt first, RanIt last, const key_type& k) const
+   {
+      const Compare &key_cmp = this->m_data.get_comp();
+      KeyOfValue key_extract;
+      RanIt lb(this->priv_lower_bound(first, last, k)), ub(lb);
+      if(lb != last && static_cast<difference_type>(!key_cmp(k, key_extract(*lb)))){
+         ++ub;
+      }
+      return std::pair<RanIt, RanIt>(lb, ub);
+   }
+
    template<class InIt>
    void priv_insert_equal_loop(InIt first, InIt last)
    {
diff --git a/include/boost/container/detail/tree.hpp b/include/boost/container/detail/tree.hpp
index 661f39c..16db841 100644
--- a/include/boost/container/detail/tree.hpp
+++ b/include/boost/container/detail/tree.hpp
@@ -1071,7 +1071,8 @@ class tree
    void clear()
    {  AllocHolder::clear(alloc_version());  }
 
-   // set operations:
+   // search operations. Const and non-const overloads even if no iterator is returned
+   // so splay implementations can to their rebalancing when searching in non-const versions
    iterator find(const key_type& k)
    {  return iterator(this->icont().find(k, KeyNodeCompare(value_comp())));  }
 
@@ -1108,6 +1109,21 @@ class tree
          (const_iterator(ret.first), const_iterator(ret.second));
    }
 
+   std::pair<iterator,iterator> lower_bound_range(const key_type& k)
+   {
+      std::pair<iiterator, iiterator> ret =
+         this->icont().lower_bound_range(k, KeyNodeCompare(value_comp()));
+      return std::pair<iterator,iterator>(iterator(ret.first), iterator(ret.second));
+   }
+
+   std::pair<const_iterator, const_iterator> lower_bound_range(const key_type& k) const
+   {
+      std::pair<iiterator, iiterator> ret =
+         this->non_const_icont().lower_bound_range(k, KeyNodeCompare(value_comp()));
+      return std::pair<const_iterator,const_iterator>
+         (const_iterator(ret.first), const_iterator(ret.second));
+   }
+
    void rebalance()
    {  intrusive_tree_proxy_t::rebalance(this->icont());   }
 
diff --git a/include/boost/container/flat_map.hpp b/include/boost/container/flat_map.hpp
index ff66e5d..0f70e0f 100644
--- a/include/boost/container/flat_map.hpp
+++ b/include/boost/container/flat_map.hpp
@@ -857,13 +857,13 @@ class flat_map
    //!
    //! <b>Complexity</b>: Logarithmic
    std::pair<iterator,iterator> equal_range(const key_type& x)
-      {  return container_detail::force_copy<std::pair<iterator,iterator> >(m_flat_tree.equal_range(x)); }
+      {  return container_detail::force_copy<std::pair<iterator,iterator> >(m_flat_tree.lower_bound_range(x)); }
 
    //! <b>Effects</b>: Equivalent to std::make_pair(this->lower_bound(k), this->upper_bound(k)).
    //!
    //! <b>Complexity</b>: Logarithmic
    std::pair<const_iterator,const_iterator> equal_range(const key_type& x) const
-      {  return container_detail::force_copy<std::pair<const_iterator,const_iterator> >(m_flat_tree.equal_range(x)); }
+      {  return container_detail::force_copy<std::pair<const_iterator,const_iterator> >(m_flat_tree.lower_bound_range(x)); }
 
    //! <b>Effects</b>: Returns true if x and y are equal
    //!
diff --git a/include/boost/container/flat_set.hpp b/include/boost/container/flat_set.hpp
index 9eedfb1..0a1ece6 100644
--- a/include/boost/container/flat_set.hpp
+++ b/include/boost/container/flat_set.hpp
@@ -604,30 +604,17 @@ class flat_set
 
    #endif   //   #if defined(BOOST_CONTAINER_DOXYGEN_INVOKED)
 
-
    //! <b>Effects</b>: Equivalent to std::make_pair(this->lower_bound(k), this->upper_bound(k)).
    //!
    //! <b>Complexity</b>: Logarithmic
    std::pair<const_iterator, const_iterator> equal_range(const key_type& x) const
-   {
-      const_iterator lb = this->lower_bound(x), ub(lb);
-      if(lb != this->cend() && static_cast<difference_type>(!this->key_comp()(x, *lb))){
-         ++ub;
-      }
-      return std::pair<const_iterator, const_iterator>(lb, ub);
-   }
+   {  return this->base_t::lower_bound_range(x);  }
 
    //! <b>Effects</b>: Equivalent to std::make_pair(this->lower_bound(k), this->upper_bound(k)).
    //!
    //! <b>Complexity</b>: Logarithmic
    std::pair<iterator,iterator> equal_range(const key_type& x)
-   {
-      iterator lb = this->lower_bound(x), ub(lb);
-      if(lb != this->end() && static_cast<difference_type>(!this->key_comp()(x, *lb))){
-         ++ub;
-      }
-      return std::pair<iterator, iterator>(lb, ub);
-   }
+   {  return this->base_t::lower_bound_range(x);  }
 
    #if defined(BOOST_CONTAINER_DOXYGEN_INVOKED)
 
diff --git a/include/boost/container/set.hpp b/include/boost/container/set.hpp
index 934d7db..ffb5d00 100644
--- a/include/boost/container/set.hpp
+++ b/include/boost/container/set.hpp
@@ -540,6 +540,22 @@ class set
    //! <b>Complexity</b>: Logarithmic
    const_iterator upper_bound(const key_type& x) const;
 
+   #endif   //#if defined(BOOST_CONTAINER_DOXYGEN_INVOKED)
+
+   //! <b>Effects</b>: Equivalent to std::make_pair(this->lower_bound(k), this->upper_bound(k)).
+   //!
+   //! <b>Complexity</b>: Logarithmic
+   std::pair<iterator,iterator> equal_range(const key_type& x)
+   {  return this->base_t::lower_bound_range(x);  }
+
+   //! <b>Effects</b>: Equivalent to std::make_pair(this->lower_bound(k), this->upper_bound(k)).
+   //!
+   //! <b>Complexity</b>: Logarithmic
+   std::pair<const_iterator, const_iterator> equal_range(const key_type& x) const
+   {  return this->base_t::lower_bound_range(x);  }
+
+   #if defined(BOOST_CONTAINER_DOXYGEN_INVOKED)
+
    //! <b>Effects</b>: Equivalent to std::make_pair(this->lower_bound(k), this->upper_bound(k)).
    //!
    //! <b>Complexity</b>: Logarithmic