diff --git a/Doxyfile b/Doxyfile
index 46139e2..a0e3b28 100644
--- a/Doxyfile
+++ b/Doxyfile
@@ -48,7 +48,7 @@ PROJECT_NAME           = fourdst::libcomposition
 # could be handy for archiving the generated documentation or if some version
 # control system is used.
 
-PROJECT_NUMBER         = v2.0.3
+PROJECT_NUMBER         = v2.0.4
 
 # Using the PROJECT_BRIEF tag one can provide an optional one line description
 # for a project that appears at the top of each page and should give viewers a
diff --git a/meson.build b/meson.build
index 998a410..9fa309e 100644
--- a/meson.build
+++ b/meson.build
@@ -18,7 +18,7 @@
 #   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 #
 # *********************************************************************** #
-project('libcomposition', 'cpp', version: 'v2.0.3', default_options: ['cpp_std=c++23'], meson_version: '>=1.5.0')
+project('libcomposition', 'cpp', version: 'v2.0.4', default_options: ['cpp_std=c++23'], meson_version: '>=1.5.0')
 
 # Add default visibility for all C++ targets
 add_project_arguments('-fvisibility=default', language: 'cpp')
diff --git a/src/composition/include/fourdst/composition/composition.h b/src/composition/include/fourdst/composition/composition.h
index be834a7..9cbf27d 100644
--- a/src/composition/include/fourdst/composition/composition.h
+++ b/src/composition/include/fourdst/composition/composition.h
@@ -94,7 +94,7 @@ namespace fourdst::composition {
      *
      */
     // ReSharper disable once CppClassCanBeFinal
-    class Composition : public CompositionAbstract {
+    class Composition final : public CompositionAbstract {
     private:
         /**
          * @struct CompositionCache
@@ -725,6 +725,8 @@ namespace fourdst::composition {
          */
         [[nodiscard]] atomic::Species getSpeciesAtIndex(size_t index) const override;
 
+        [[nodiscard]] std::unique_ptr<CompositionAbstract> clone() const override;
+
         /**
          * @brief Overloaded output stream operator for Composition.
          * @param os The output stream.
@@ -750,7 +752,7 @@ namespace fourdst::composition {
          * for species are defined based on their atomic mass. When iterating over the molar abundance map, species will be
          * seen in order from lightest to heaviest.
          */
-        auto begin() {
+        [[nodiscard]] std::map<atomic::Species, double>::iterator begin() override {
             return m_molarAbundances.begin();
         }
 
@@ -771,7 +773,7 @@ namespace fourdst::composition {
          * for species are defined based on their atomic mass. When iterating over the molar abundance map, species will be
          * seen in order from lightest to heaviest.
          */
-        [[nodiscard]] auto begin() const {
+        [[nodiscard]] std::map<atomic::Species, double>::const_iterator begin() const override {
             return m_molarAbundances.cbegin();
         }
 
@@ -792,7 +794,7 @@ namespace fourdst::composition {
          * for species are defined based on their atomic mass. When iterating over the molar abundance map, species will be
          * seen in order from lightest to heaviest.
          */
-        auto end() {
+        [[nodiscard]] std::map<atomic::Species, double>::iterator end() override {
             return m_molarAbundances.end();
         }
 
@@ -813,7 +815,7 @@ namespace fourdst::composition {
          * for species are defined based on their atomic mass. When iterating over the molar abundance map, species will be
          * seen in order from lightest to heaviest.
          */
-        [[nodiscard]] auto end() const {
+        [[nodiscard]] std::map<atomic::Species, double>::const_iterator end() const override {
             return m_molarAbundances.cend();
         }
 
diff --git a/src/composition/include/fourdst/composition/composition_abstract.h b/src/composition/include/fourdst/composition/composition_abstract.h
index 38caa73..173fd01 100644
--- a/src/composition/include/fourdst/composition/composition_abstract.h
+++ b/src/composition/include/fourdst/composition/composition_abstract.h
@@ -169,7 +169,14 @@ namespace fourdst::composition {
          * @param index The index of the species.
          * @return The atomic species at the specified index.
          */
-        [[nodiscard]] virtual fourdst::atomic::Species getSpeciesAtIndex(size_t index) const = 0;
+        [[nodiscard]] virtual atomic::Species getSpeciesAtIndex(size_t index) const = 0;
+
+        [[nodiscard]] virtual std::unique_ptr<CompositionAbstract> clone() const = 0;
+
+        [[nodiscard]] virtual std::map<atomic::Species, double>::iterator begin() = 0;
+        [[nodiscard]] virtual std::map<atomic::Species, double>::iterator end() = 0;
+        [[nodiscard]] virtual std::map<atomic::Species, double>::const_iterator begin() const = 0;
+        [[nodiscard]] virtual std::map<atomic::Species, double>::const_iterator end() const = 0;
     };
 
     // ReSharper disable once CppClassCanBeFinal
@@ -197,6 +204,21 @@ namespace fourdst::composition {
         [[nodiscard]] size_t getSpeciesIndex(const std::string& symbol) const override { return m_base_composition->getSpeciesIndex(symbol); };
         [[nodiscard]] size_t getSpeciesIndex(const atomic::Species& species) const override { return m_base_composition->getSpeciesIndex(species); };
         [[nodiscard]] atomic::Species getSpeciesAtIndex(const size_t index) const override { return m_base_composition->getSpeciesAtIndex(index); };
+        [[nodiscard]] std::unique_ptr<CompositionAbstract> clone() const override {
+            return std::make_unique<CompositionDecorator>(m_base_composition->clone());
+        }
+        [[nodiscard]] std::map<atomic::Species, double>::iterator begin() override {
+            return m_base_composition->begin();
+        }
+        [[nodiscard]] std::map<atomic::Species, double>::iterator end() override {
+            return m_base_composition->end();
+        }
+        [[nodiscard]] std::map<atomic::Species, double>::const_iterator begin() const override {
+            return std::as_const(*m_base_composition).begin();
+        }
+        [[nodiscard]] std::map<atomic::Species, double>::const_iterator end() const override {
+            return std::as_const(*m_base_composition).end();
+        }
     private:
         std::unique_ptr<CompositionAbstract> m_base_composition;
     };
diff --git a/src/composition/lib/composition.cpp b/src/composition/lib/composition.cpp
index b1e17fe..3f48c82 100644
--- a/src/composition/lib/composition.cpp
+++ b/src/composition/lib/composition.cpp
@@ -506,6 +506,10 @@ namespace fourdst::composition {
         return sortedSymbols.at(index);
     }
 
+    std::unique_ptr<CompositionAbstract> Composition::clone() const {
+        return std::make_unique<Composition>(*this);
+    }
+
     bool Composition::contains(
         const atomic::Species &species
     ) const noexcept {