diff --git a/Assets/UniGLTF/Runtime/AssemblyInfo.cs b/Assets/UniGLTF/Runtime/AssemblyInfo.cs
new file mode 100644
index 000000000..67e2c8115
--- /dev/null
+++ b/Assets/UniGLTF/Runtime/AssemblyInfo.cs
@@ -0,0 +1,5 @@
+#if UNITY_EDITOR
+using System.Runtime.CompilerServices;
+
+[assembly: InternalsVisibleTo("UniGLTF.Tests")]
+#endif
\ No newline at end of file
diff --git a/Assets/UniGLTF/Runtime/AssemblyInfo.cs.meta b/Assets/UniGLTF/Runtime/AssemblyInfo.cs.meta
new file mode 100644
index 000000000..97a459ad4
--- /dev/null
+++ b/Assets/UniGLTF/Runtime/AssemblyInfo.cs.meta
@@ -0,0 +1,11 @@
+fileFormatVersion: 2
+guid: 7aed15fa830416246b0c408322cd4099
+MonoImporter:
+  externalObjects: {}
+  serializedVersion: 2
+  defaultReferences: []
+  executionOrder: 0
+  icon: {instanceID: 0}
+  userData: 
+  assetBundleName: 
+  assetBundleVariant: 
diff --git a/Assets/UniGLTF/Runtime/UniGLTF/IO/MeshIO/MeshData.cs b/Assets/UniGLTF/Runtime/UniGLTF/IO/MeshIO/MeshData.cs
index 387e32eff..55097373c 100644
--- a/Assets/UniGLTF/Runtime/UniGLTF/IO/MeshIO/MeshData.cs
+++ b/Assets/UniGLTF/Runtime/UniGLTF/IO/MeshIO/MeshData.cs
@@ -8,7 +8,7 @@ using UnityEngine.Rendering;
 
 namespace UniGLTF
 {
-    public class MeshData : IDisposable
+    internal class MeshData : IDisposable
     {
         private NativeArray<MeshVertex> _vertices;
         public NativeArray<MeshVertex> Vertices => _vertices.GetSubArray(0, _currentVertexCount);
diff --git a/Assets/UniGLTF/Runtime/UniGLTF/IO/MeshIO/MeshVertex.cs b/Assets/UniGLTF/Runtime/UniGLTF/IO/MeshIO/MeshVertex.cs
index 5a8bc0f45..5619fa84d 100644
--- a/Assets/UniGLTF/Runtime/UniGLTF/IO/MeshIO/MeshVertex.cs
+++ b/Assets/UniGLTF/Runtime/UniGLTF/IO/MeshIO/MeshVertex.cs
@@ -11,7 +11,7 @@ namespace UniGLTF
     /// そのままGPUにアップロードされる
     /// </summary>
     [Serializable, StructLayout(LayoutKind.Sequential)]
-    public readonly struct MeshVertex
+    internal readonly struct MeshVertex
     {
         private readonly Vector3 _position;
         private readonly Vector3 _normal;
diff --git a/Assets/UniGLTF/Runtime/UniGLTF/IO/MeshIO/SkinnedMeshVertex.cs b/Assets/UniGLTF/Runtime/UniGLTF/IO/MeshIO/SkinnedMeshVertex.cs
index a59d0fff9..5850aff65 100644
--- a/Assets/UniGLTF/Runtime/UniGLTF/IO/MeshIO/SkinnedMeshVertex.cs
+++ b/Assets/UniGLTF/Runtime/UniGLTF/IO/MeshIO/SkinnedMeshVertex.cs
@@ -9,7 +9,7 @@ namespace UniGLTF
     /// そのままGPUにアップロードされる
     /// </summary>
     [Serializable, StructLayout(LayoutKind.Sequential)]
-    public readonly struct SkinnedMeshVertex
+    internal readonly struct SkinnedMeshVertex
     {
         private readonly float _boneWeight0;
         private readonly float _boneWeight1;