diff --git a/libcxx/include/CMakeLists.txt b/libcxx/include/CMakeLists.txt
--- a/libcxx/include/CMakeLists.txt
+++ b/libcxx/include/CMakeLists.txt
@@ -886,10 +886,12 @@
   experimental/__config
   experimental/__memory
   experimental/__simd/abi_tag.h
+  experimental/__simd/declaration.h
   experimental/__simd/scalar.h
   experimental/__simd/simd.h
   experimental/__simd/simd_mask.h
   experimental/__simd/traits.h
+  experimental/__simd/utility.h
   experimental/__simd/vec_ext.h
   experimental/deque
   experimental/forward_list
diff --git a/libcxx/include/experimental/__simd/simd.h b/libcxx/include/experimental/__simd/declaration.h
copy from libcxx/include/experimental/__simd/simd.h
copy to libcxx/include/experimental/__simd/declaration.h
--- a/libcxx/include/experimental/__simd/simd.h
+++ b/libcxx/include/experimental/__simd/declaration.h
@@ -7,29 +7,22 @@
 //
 //===----------------------------------------------------------------------===//
 
-#ifndef _LIBCPP_EXPERIMENTAL___SIMD_SIMD_H
-#define _LIBCPP_EXPERIMENTAL___SIMD_SIMD_H
-
-#include <experimental/__simd/abi_tag.h>
+#ifndef _LIBCPP_EXPERIMENTAL___SIMD_DECLARATION_H
+#define _LIBCPP_EXPERIMENTAL___SIMD_DECLARATION_H
 
 #if _LIBCPP_STD_VER >= 17 && defined(_LIBCPP_ENABLE_EXPERIMENTAL)
 
 _LIBCPP_BEGIN_NAMESPACE_EXPERIMENTAL
 inline namespace parallelism_v2 {
 
-// class template simd [simd.class]
-// TODO: implement simd class
 template <class _Tp, class _Abi = simd_abi::compatible<_Tp>>
 class simd;
 
-template <class _Tp>
-using native_simd = simd<_Tp, simd_abi::native<_Tp>>;
-
-template <class _Tp, int _Np>
-using fixed_size_simd = simd<_Tp, simd_abi::fixed_size<_Np>>;
+template <class _Tp, class _Abi = simd_abi::compatible<_Tp>>
+class simd_mask;
 
 } // namespace parallelism_v2
 _LIBCPP_END_NAMESPACE_EXPERIMENTAL
 
 #endif // _LIBCPP_STD_VER >= 17 && defined(_LIBCPP_ENABLE_EXPERIMENTAL)
-#endif // _LIBCPP_EXPERIMENTAL___SIMD_SIMD_H
+#endif // _LIBCPP_EXPERIMENTAL___SIMD_DECLARATION_H
diff --git a/libcxx/include/experimental/__simd/simd.h b/libcxx/include/experimental/__simd/simd.h
--- a/libcxx/include/experimental/__simd/simd.h
+++ b/libcxx/include/experimental/__simd/simd.h
@@ -11,6 +11,8 @@
 #define _LIBCPP_EXPERIMENTAL___SIMD_SIMD_H
 
 #include <experimental/__simd/abi_tag.h>
+#include <experimental/__simd/declaration.h>
+#include <experimental/__simd/traits.h>
 
 #if _LIBCPP_STD_VER >= 17 && defined(_LIBCPP_ENABLE_EXPERIMENTAL)
 
@@ -19,8 +21,15 @@
 
 // class template simd [simd.class]
 // TODO: implement simd class
-template <class _Tp, class _Abi = simd_abi::compatible<_Tp>>
-class simd;
+template <class _Tp, class _Abi>
+class simd {
+public:
+  using value_type = _Tp;
+  using mask_type  = simd_mask<_Tp, _Abi>;
+  using abi_type   = _Abi;
+
+  static _LIBCPP_HIDE_FROM_ABI constexpr size_t size() noexcept { return simd_size_v<value_type, abi_type>; }
+};
 
 template <class _Tp>
 using native_simd = simd<_Tp, simd_abi::native<_Tp>>;
diff --git a/libcxx/include/experimental/__simd/simd_mask.h b/libcxx/include/experimental/__simd/simd_mask.h
--- a/libcxx/include/experimental/__simd/simd_mask.h
+++ b/libcxx/include/experimental/__simd/simd_mask.h
@@ -11,6 +11,7 @@
 #define _LIBCPP_EXPERIMENTAL___SIMD_SIMD_MASK_H
 
 #include <experimental/__simd/abi_tag.h>
+#include <experimental/__simd/declaration.h>
 
 #if _LIBCPP_STD_VER >= 17 && defined(_LIBCPP_ENABLE_EXPERIMENTAL)
 
@@ -19,8 +20,15 @@
 
 // class template simd_mask [simd.mask.class]
 // TODO: implement simd_mask class
-template <class _Tp, class _Abi = simd_abi::compatible<_Tp>>
-class simd_mask;
+template <class _Tp, class _Abi>
+class simd_mask {
+public:
+  using value_type = bool;
+  using simd_type  = simd<_Tp, _Abi>;
+  using abi_type   = _Abi;
+
+  static _LIBCPP_HIDE_FROM_ABI constexpr size_t size() noexcept { return simd_type::size(); }
+};
 
 template <class _Tp>
 using native_simd_mask = simd_mask<_Tp, simd_abi::native<_Tp>>;
diff --git a/libcxx/include/experimental/__simd/traits.h b/libcxx/include/experimental/__simd/traits.h
--- a/libcxx/include/experimental/__simd/traits.h
+++ b/libcxx/include/experimental/__simd/traits.h
@@ -11,8 +11,8 @@
 #define _LIBCPP_EXPERIMENTAL___SIMD_TRAITS_H
 
 #include <experimental/__simd/abi_tag.h>
-#include <experimental/__simd/simd.h>
-#include <experimental/__simd/simd_mask.h>
+#include <experimental/__simd/declaration.h>
+#include <experimental/__simd/utility.h>
 
 #if _LIBCPP_STD_VER >= 17 && defined(_LIBCPP_ENABLE_EXPERIMENTAL)
 
@@ -50,6 +50,14 @@
 template <class _Tp>
 struct is_simd_mask : bool_constant<is_simd_mask_v<_Tp>> {};
 
+template <class _Tp,
+          class _Abi = simd_abi::compatible<_Tp>,
+          class      = enable_if_t<__is_vectorizable<_Tp>() && is_abi_tag_v<_Abi>>>
+inline constexpr size_t simd_size_v = _Abi::__simd_size;
+
+template <class _Tp, class _Abi = simd_abi::compatible<_Tp>>
+struct simd_size : integral_constant<size_t, simd_size_v<_Tp, _Abi>> {};
+
 } // namespace parallelism_v2
 _LIBCPP_END_NAMESPACE_EXPERIMENTAL
 
diff --git a/libcxx/include/experimental/__simd/simd.h b/libcxx/include/experimental/__simd/utility.h
copy from libcxx/include/experimental/__simd/simd.h
copy to libcxx/include/experimental/__simd/utility.h
--- a/libcxx/include/experimental/__simd/simd.h
+++ b/libcxx/include/experimental/__simd/utility.h
@@ -7,29 +7,21 @@
 //
 //===----------------------------------------------------------------------===//
 
-#ifndef _LIBCPP_EXPERIMENTAL___SIMD_SIMD_H
-#define _LIBCPP_EXPERIMENTAL___SIMD_SIMD_H
+#ifndef _LIBCPP_EXPERIMENTAL___SIMD_UTILITY_H
+#define _LIBCPP_EXPERIMENTAL___SIMD_UTILITY_H
 
-#include <experimental/__simd/abi_tag.h>
+#include <type_traits>
 
 #if _LIBCPP_STD_VER >= 17 && defined(_LIBCPP_ENABLE_EXPERIMENTAL)
 
 _LIBCPP_BEGIN_NAMESPACE_EXPERIMENTAL
 inline namespace parallelism_v2 {
-
-// class template simd [simd.class]
-// TODO: implement simd class
-template <class _Tp, class _Abi = simd_abi::compatible<_Tp>>
-class simd;
-
 template <class _Tp>
-using native_simd = simd<_Tp, simd_abi::native<_Tp>>;
-
-template <class _Tp, int _Np>
-using fixed_size_simd = simd<_Tp, simd_abi::fixed_size<_Np>>;
-
+_LIBCPP_HIDE_FROM_ABI constexpr bool __is_vectorizable() {
+  return is_arithmetic_v<_Tp> && !is_const_v<_Tp> && !is_volatile_v<_Tp> && !is_same_v<_Tp, bool>;
+}
 } // namespace parallelism_v2
 _LIBCPP_END_NAMESPACE_EXPERIMENTAL
 
 #endif // _LIBCPP_STD_VER >= 17 && defined(_LIBCPP_ENABLE_EXPERIMENTAL)
-#endif // _LIBCPP_EXPERIMENTAL___SIMD_SIMD_H
+#endif // _LIBCPP_EXPERIMENTAL___SIMD_UTILITY_H
diff --git a/libcxx/include/experimental/simd b/libcxx/include/experimental/simd
--- a/libcxx/include/experimental/simd
+++ b/libcxx/include/experimental/simd
@@ -47,6 +47,10 @@
   template <class T> struct is_simd_mask;
   template <class T> inline constexpr bool is_simd_mask_v = is_simd_mask<T>::value;
 
+  template<class T, class Abi = simd_abi::compatible<T>> struct simd_size;
+  template<class T, class Abi = simd_abi::compatible<T>>
+    inline constexpr size_t simd_size_v = simd_size<T,Abi>::value;
+
 } // namespace parallelism_v2
 } // namespace std::experimental
 
diff --git a/libcxx/test/libcxx/transitive_includes/cxx03.csv b/libcxx/test/libcxx/transitive_includes/cxx03.csv
--- a/libcxx/test/libcxx/transitive_includes/cxx03.csv
+++ b/libcxx/test/libcxx/transitive_includes/cxx03.csv
@@ -262,6 +262,7 @@
 experimental/set experimental/memory_resource
 experimental/set set
 experimental/simd cstddef
+experimental/simd type_traits
 experimental/string experimental/memory_resource
 experimental/string string
 experimental/unordered_map algorithm
diff --git a/libcxx/test/libcxx/transitive_includes/cxx11.csv b/libcxx/test/libcxx/transitive_includes/cxx11.csv
--- a/libcxx/test/libcxx/transitive_includes/cxx11.csv
+++ b/libcxx/test/libcxx/transitive_includes/cxx11.csv
@@ -262,6 +262,7 @@
 experimental/set experimental/memory_resource
 experimental/set set
 experimental/simd cstddef
+experimental/simd type_traits
 experimental/string experimental/memory_resource
 experimental/string string
 experimental/unordered_map algorithm
diff --git a/libcxx/test/libcxx/transitive_includes/cxx14.csv b/libcxx/test/libcxx/transitive_includes/cxx14.csv
--- a/libcxx/test/libcxx/transitive_includes/cxx14.csv
+++ b/libcxx/test/libcxx/transitive_includes/cxx14.csv
@@ -262,6 +262,7 @@
 experimental/set experimental/memory_resource
 experimental/set set
 experimental/simd cstddef
+experimental/simd type_traits
 experimental/string experimental/memory_resource
 experimental/string string
 experimental/type_traits initializer_list
diff --git a/libcxx/test/libcxx/transitive_includes/cxx17.csv b/libcxx/test/libcxx/transitive_includes/cxx17.csv
--- a/libcxx/test/libcxx/transitive_includes/cxx17.csv
+++ b/libcxx/test/libcxx/transitive_includes/cxx17.csv
@@ -262,6 +262,7 @@
 experimental/set experimental/memory_resource
 experimental/set set
 experimental/simd cstddef
+experimental/simd type_traits
 experimental/string experimental/memory_resource
 experimental/string string
 experimental/type_traits initializer_list
diff --git a/libcxx/test/libcxx/transitive_includes/cxx20.csv b/libcxx/test/libcxx/transitive_includes/cxx20.csv
--- a/libcxx/test/libcxx/transitive_includes/cxx20.csv
+++ b/libcxx/test/libcxx/transitive_includes/cxx20.csv
@@ -269,6 +269,7 @@
 experimental/set experimental/memory_resource
 experimental/set set
 experimental/simd cstddef
+experimental/simd type_traits
 experimental/string experimental/memory_resource
 experimental/string string
 experimental/type_traits initializer_list
diff --git a/libcxx/test/libcxx/transitive_includes/cxx23.csv b/libcxx/test/libcxx/transitive_includes/cxx23.csv
--- a/libcxx/test/libcxx/transitive_includes/cxx23.csv
+++ b/libcxx/test/libcxx/transitive_includes/cxx23.csv
@@ -175,6 +175,7 @@
 experimental/set experimental/memory_resource
 experimental/set set
 experimental/simd cstddef
+experimental/simd type_traits
 experimental/string experimental/memory_resource
 experimental/string string
 experimental/type_traits initializer_list
diff --git a/libcxx/test/libcxx/transitive_includes/cxx26.csv b/libcxx/test/libcxx/transitive_includes/cxx26.csv
--- a/libcxx/test/libcxx/transitive_includes/cxx26.csv
+++ b/libcxx/test/libcxx/transitive_includes/cxx26.csv
@@ -175,6 +175,7 @@
 experimental/set experimental/memory_resource
 experimental/set set
 experimental/simd cstddef
+experimental/simd type_traits
 experimental/string experimental/memory_resource
 experimental/string string
 experimental/type_traits initializer_list
diff --git a/libcxx/test/std/experimental/simd/simd.class/simd_width.pass.cpp b/libcxx/test/std/experimental/simd/simd.class/simd_width.pass.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/std/experimental/simd/simd.class/simd_width.pass.cpp
@@ -0,0 +1,38 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14
+
+// <experimental/simd>
+//
+// [simd.class]
+// static constexpr size_t size() noexcept;
+
+#include "../test_utils.h"
+#include <experimental/simd>
+
+namespace ex = std::experimental::parallelism_v2;
+struct CheckSimdWidth {
+  template <class _Tp, class SimdAbi>
+  void operator()() {
+    const ex::simd<_Tp, SimdAbi> origin_simd{};
+    static_assert(origin_simd.size() == ex::simd_size_v<_Tp, SimdAbi>);
+  }
+};
+template <class F, std::size_t _Np, class _Tp>
+void test_simd_abi() {}
+template <class F, std::size_t _Np, class _Tp, class SimdAbi, class... SimdAbis>
+void test_simd_abi() {
+  F{}.template operator()<_Tp, SimdAbi>();
+  test_simd_abi<F, _Np, _Tp, SimdAbis...>();
+}
+
+int main(int, char**) {
+  test_all_simd_abi<CheckSimdWidth>();
+  return 0;
+}
diff --git a/libcxx/test/std/experimental/simd/simd.mask.class/simd_mask_width.pass.cpp b/libcxx/test/std/experimental/simd/simd.mask.class/simd_mask_width.pass.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/std/experimental/simd/simd.mask.class/simd_mask_width.pass.cpp
@@ -0,0 +1,38 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14
+
+// <experimental/simd>
+//
+// [simd.mask.class]
+// static constexpr size_t size() noexcept;
+
+#include "../test_utils.h"
+#include <experimental/simd>
+
+namespace ex = std::experimental::parallelism_v2;
+struct CheckSimdMaskWidth {
+  template <class _Tp, class SimdAbi>
+  void operator()() {
+    const ex::simd_mask<_Tp, SimdAbi> origin_simd_mask{};
+    static_assert(origin_simd_mask.size() == ex::simd_size_v<_Tp, SimdAbi>);
+  }
+};
+template <class F, std::size_t _Np, class _Tp>
+void test_simd_abi() {}
+template <class F, std::size_t _Np, class _Tp, class SimdAbi, class... SimdAbis>
+void test_simd_abi() {
+  F{}.template operator()<_Tp, SimdAbi>();
+  test_simd_abi<F, _Np, _Tp, SimdAbis...>();
+}
+
+int main(int, char**) {
+  test_all_simd_abi<CheckSimdMaskWidth>();
+  return 0;
+}
diff --git a/libcxx/test/std/experimental/simd/simd.traits/simd_size.pass.cpp b/libcxx/test/std/experimental/simd/simd.traits/simd_size.pass.cpp
new file mode 100644
--- /dev/null
+++ b/libcxx/test/std/experimental/simd/simd.traits/simd_size.pass.cpp
@@ -0,0 +1,120 @@
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14
+
+// <experimental/simd>
+//
+// [simd.traits]
+//template <class T, class Abi = simd_abi::compatible<T>> struct simd_size;
+//template <class T, class Abi = simd_abi::compatible<T>>
+//inline constexpr size_t ex::simd_size_v = ex::simd_size<T, Abi>::value;
+
+#include "../test_utils.h"
+#include <experimental/simd>
+
+namespace ex = std::experimental::parallelism_v2;
+
+struct CheckSimdSizeScalar {
+  template <class _Tp, class SimdAbi>
+  void operator()() {
+    static_assert(ex::simd_size<_Tp, SimdAbi>::value == 1);
+  };
+};
+struct CheckSimdSizeVScalar {
+  template <class _Tp, class SimdAbi>
+  void operator()() {
+    static_assert(ex::simd_size_v<_Tp, SimdAbi> == 1);
+  };
+};
+struct CheckSimdSizeDeduce {
+  template <class _Tp, class SimdAbi, size_t _Np>
+  void operator()() {
+    static_assert(ex::simd_size<_Tp, SimdAbi>::value == _Np);
+  };
+};
+struct CheckSimdSizeVDeduce {
+  template <class _Tp, class SimdAbi, size_t _Np>
+  void operator()() {
+    static_assert(ex::simd_size_v<_Tp, SimdAbi> == _Np);
+  };
+};
+struct CheckSimdSizeFixedSize {
+  template <class _Tp, class SimdAbi, size_t _Np>
+  void operator()() {
+    static_assert(ex::simd_size<_Tp, SimdAbi>::value == _Np);
+  };
+};
+struct CheckSimdSizeVFixedSize {
+  template <class _Tp, class SimdAbi, size_t _Np>
+  void operator()() {
+    static_assert(ex::simd_size_v<_Tp, SimdAbi> == _Np);
+  };
+};
+struct CheckSimdSizeCompatible {
+  template <class _Tp, class SimdAbi>
+  void operator()() {
+    static_assert(ex::simd_size<_Tp, SimdAbi>::value == 16 / sizeof(_Tp));
+  };
+};
+struct CheckSimdSizeVCompatible {
+  template <class _Tp, class SimdAbi>
+  void operator()() {
+    static_assert(ex::simd_size_v<_Tp, SimdAbi> == 16 / sizeof(_Tp));
+  };
+};
+
+struct CheckSimdSizeNative {
+  template <class _Tp, class SimdAbi>
+  void operator()() {
+    static_assert(ex::simd_size<_Tp, SimdAbi>::value == _LIBCPP_NATIVE_SIMD_WIDTH_IN_BYTES / sizeof(_Tp));
+  };
+};
+struct CheckSimdSizeVNative {
+  template <class _Tp, class SimdAbi>
+  void operator()() {
+    static_assert(ex::simd_size_v<_Tp, SimdAbi> == _LIBCPP_NATIVE_SIMD_WIDTH_IN_BYTES / sizeof(_Tp));
+  };
+};
+
+template <class F, std::size_t _Np, class _Tp>
+void test_simd_abi() {}
+template <class F, std::size_t _Np, class _Tp, class SimdAbi, class... SimdAbis>
+void test_simd_abi() {
+  if constexpr (std::is_same_v<F, CheckSimdSizeScalar> || std::is_same_v<F, CheckSimdSizeVScalar>) {
+    F{}.template operator()<_Tp, ex::simd_abi::scalar>();
+  } else if constexpr (std::is_same_v<F, CheckSimdSizeDeduce> || std::is_same_v<F, CheckSimdSizeVDeduce>) {
+    F{}.template operator()<_Tp, ex::simd_abi::deduce_t<_Tp, _Np>, _Np>();
+  } else if constexpr (std::is_same_v<F, CheckSimdSizeFixedSize> || std::is_same_v<F, CheckSimdSizeVFixedSize>) {
+    F{}.template operator()<_Tp, ex::simd_abi::fixed_size<_Np>, _Np>();
+  } else if constexpr (std::is_same_v<F, CheckSimdSizeCompatible> || std::is_same_v<F, CheckSimdSizeVCompatible>) {
+    F{}.template operator()<_Tp, ex::simd_abi::compatible<_Tp>>();
+  } else {
+    F{}.template operator()<_Tp, ex::simd_abi::native<_Tp>>();
+  }
+  test_simd_abi<F, _Np, _Tp, SimdAbis...>();
+}
+
+int main(int, char**) {
+  test_all_simd_abi<CheckSimdSizeScalar>();
+  test_all_simd_abi<CheckSimdSizeVScalar>();
+
+  test_all_simd_abi<CheckSimdSizeDeduce>();
+  test_all_simd_abi<CheckSimdSizeVDeduce>();
+
+  test_all_simd_abi<CheckSimdSizeFixedSize>();
+  test_all_simd_abi<CheckSimdSizeVFixedSize>();
+
+  test_all_simd_abi<CheckSimdSizeCompatible>();
+  test_all_simd_abi<CheckSimdSizeVCompatible>();
+
+  test_all_simd_abi<CheckSimdSizeNative>();
+  test_all_simd_abi<CheckSimdSizeVNative>();
+
+  return 0;
+}