diff --git a/src/Umbraco.Core/IO/IFileSystemExtensions.cs b/src/Umbraco.Core/IO/FileSystemExtensions.cs
similarity index 57%
rename from src/Umbraco.Core/IO/IFileSystemExtensions.cs
rename to src/Umbraco.Core/IO/FileSystemExtensions.cs
index 516049a146..fdf3a7dd0a 100644
--- a/src/Umbraco.Core/IO/IFileSystemExtensions.cs
+++ b/src/Umbraco.Core/IO/FileSystemExtensions.cs
@@ -2,11 +2,14 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
+using Umbraco.Core.CodeAnnotations;
 
 namespace Umbraco.Core.IO
 {
-    public static class IFileSystemExtensions
+	[UmbracoExperimentalFeature("http://issues.umbraco.org/issue/U4-1156", "Will be declared public after 4.10")]
+    public static class FileSystemExtensions
     {
+		[UmbracoExperimentalFeature("", "Will be declared public after 4.10")]
         internal static long GetSize(this IFileSystem fs, string path)
         {
             var s = fs.OpenFile(path);
@@ -16,6 +19,7 @@ namespace Umbraco.Core.IO
             return size;
         }
 
+		[UmbracoExperimentalFeature("", "Will be declared public after 4.10")]
         internal static void CopyFile(this IFileSystem fs, string path, string newPath)
         {
             fs.AddFile(newPath, fs.OpenFile(path));
diff --git a/src/Umbraco.Core/IO/FileSystemProvider.cs b/src/Umbraco.Core/IO/FileSystemProvider.cs
index 31f767f28e..1f6013078f 100644
--- a/src/Umbraco.Core/IO/FileSystemProvider.cs
+++ b/src/Umbraco.Core/IO/FileSystemProvider.cs
@@ -2,9 +2,11 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
+using Umbraco.Core.CodeAnnotations;
 
 namespace Umbraco.Core.IO
 {
+	[UmbracoExperimentalFeature("http://issues.umbraco.org/issue/U4-1156", "Will be declared public after 4.10")]
     internal class FileSystemProvider
     {
         public const string Media = "media";
diff --git a/src/Umbraco.Core/IO/FileSystemProviderAttribute.cs b/src/Umbraco.Core/IO/FileSystemProviderAttribute.cs
index 4d09bc4f1e..39bb8db8dc 100644
--- a/src/Umbraco.Core/IO/FileSystemProviderAttribute.cs
+++ b/src/Umbraco.Core/IO/FileSystemProviderAttribute.cs
@@ -2,9 +2,11 @@
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
+using Umbraco.Core.CodeAnnotations;
 
 namespace Umbraco.Core.IO
 {
+	[UmbracoExperimentalFeature("http://issues.umbraco.org/issue/U4-1156", "Will be declared public after 4.10")]
     [AttributeUsage(AttributeTargets.Class, AllowMultiple = false, Inherited = false)]
     internal class FileSystemProviderAttribute : Attribute
     {
diff --git a/src/Umbraco.Core/IO/FileSystemProviderManager.cs b/src/Umbraco.Core/IO/FileSystemProviderManager.cs
index 99d9eb5833..5654e764d6 100644
--- a/src/Umbraco.Core/IO/FileSystemProviderManager.cs
+++ b/src/Umbraco.Core/IO/FileSystemProviderManager.cs
@@ -5,10 +5,12 @@ using System.Configuration;
 using System.Linq;
 using System.Reflection;
 using System.Text;
+using Umbraco.Core.CodeAnnotations;
 using Umbraco.Core.Configuration;
 
 namespace Umbraco.Core.IO
 {
+	[UmbracoExperimentalFeature("http://issues.umbraco.org/issue/U4-1156", "Will be declared public after 4.10")]
     internal class FileSystemProviderManager
     {
         private readonly FileSystemProvidersSection _config;
diff --git a/src/Umbraco.Core/IO/FileSystemWrapper.cs b/src/Umbraco.Core/IO/FileSystemWrapper.cs
index f0fcff213d..236a79a380 100644
--- a/src/Umbraco.Core/IO/FileSystemWrapper.cs
+++ b/src/Umbraco.Core/IO/FileSystemWrapper.cs
@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
+using Umbraco.Core.CodeAnnotations;
 
 namespace Umbraco.Core.IO
 {
@@ -14,6 +15,7 @@ namespace Umbraco.Core.IO
 	/// 
 	/// This abstract class just wraps the 'real' IFileSystem object passed in to its constructor.
 	/// </remarks>
+	[UmbracoExperimentalFeature("http://issues.umbraco.org/issue/U4-1156", "Will be declared public after 4.10")]
 	internal abstract class FileSystemWrapper : IFileSystem
 	{
 		private readonly IFileSystem _wrapped;
diff --git a/src/Umbraco.Core/IO/IFileSystem.cs b/src/Umbraco.Core/IO/IFileSystem.cs
index 2c11d290d0..d0e7490890 100644
--- a/src/Umbraco.Core/IO/IFileSystem.cs
+++ b/src/Umbraco.Core/IO/IFileSystem.cs
@@ -1,9 +1,11 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
+using Umbraco.Core.CodeAnnotations;
 
 namespace Umbraco.Core.IO
 {
+	[UmbracoExperimentalFeature("http://issues.umbraco.org/issue/U4-1156", "Will be declared public after 4.10")]
     internal interface IFileSystem
     {
         IEnumerable<string> GetDirectories(string path);
diff --git a/src/Umbraco.Core/IO/MediaFileSystem.cs b/src/Umbraco.Core/IO/MediaFileSystem.cs
index 3c8b3429b6..0193f7480a 100644
--- a/src/Umbraco.Core/IO/MediaFileSystem.cs
+++ b/src/Umbraco.Core/IO/MediaFileSystem.cs
@@ -1,5 +1,9 @@
-using System.Linq;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
 using System.Text;
+using Umbraco.Core.CodeAnnotations;
+using Umbraco.Core.Configuration;
 
 namespace Umbraco.Core.IO
 {
@@ -7,11 +11,47 @@ namespace Umbraco.Core.IO
 	/// A custom file system provider for media
 	/// </summary>
 	[FileSystemProvider("media")]
+	[UmbracoExperimentalFeature("http://issues.umbraco.org/issue/U4-1156", "Will be declared public after 4.10")]
 	internal class MediaFileSystem : FileSystemWrapper
 	{
 		public MediaFileSystem(IFileSystem wrapped)
 			: base(wrapped)
 		{
 		}
+
+		public string GetRelativePath(int propertyId, string fileName)
+		{
+			var seperator = UmbracoSettings.UploadAllowDirectories
+				? Path.DirectorySeparatorChar
+				: '-';
+
+			return propertyId.ToString() + seperator + fileName;
+		}
+
+		public IEnumerable<string> GetThumbnails(string path)
+		{
+			var parentDirectory = System.IO.Path.GetDirectoryName(path);
+			var extension = System.IO.Path.GetExtension(path);
+
+			return GetFiles(parentDirectory)
+				.Where(x => x.StartsWith(path.TrimEnd(extension) + "_thumb"))
+				.ToList();
+		}
+
+		public void DeleteFile(string path, bool deleteThumbnails)
+		{
+			DeleteFile(path);
+
+			if (!deleteThumbnails)
+				return;
+
+			DeleteThumbnails(path);
+		}
+
+		public void DeleteThumbnails(string path)
+		{
+			GetThumbnails(path)
+				.ForEach(DeleteFile);
+		}
 	}
 }
diff --git a/src/Umbraco.Core/IO/MediaFileSystemExtensions.cs b/src/Umbraco.Core/IO/MediaFileSystemExtensions.cs
deleted file mode 100644
index 3fb79fff4e..0000000000
--- a/src/Umbraco.Core/IO/MediaFileSystemExtensions.cs
+++ /dev/null
@@ -1,47 +0,0 @@
-using System;
-using System.Collections.Generic;
-using System.IO;
-using System.Linq;
-using System.Text;
-using Umbraco.Core.Configuration;
-
-namespace Umbraco.Core.IO
-{
-    public static class MediaFileSystemExtensions
-    {
-        internal static string GetRelativePath(this MediaFileSystem fs, int propertyId, string fileName)
-        {
-            var seperator = UmbracoSettings.UploadAllowDirectories
-                ? Path.DirectorySeparatorChar 
-                : '-';
-
-            return propertyId.ToString() + seperator + fileName;
-        }
-
-        internal static IEnumerable<string> GetThumbnails(this MediaFileSystem fs, string path)
-        {
-            var parentDirectory = System.IO.Path.GetDirectoryName(path);
-            var extension = System.IO.Path.GetExtension(path);
-
-            return fs.GetFiles(parentDirectory)
-                .Where(x => x.StartsWith(path.TrimEnd(extension) + "_thumb"))
-                .ToList();
-        }
-
-        internal static void DeleteFile(this MediaFileSystem fs, string path, bool deleteThumbnails)
-        {
-            fs.DeleteFile(path);
-
-            if(!deleteThumbnails)
-                return;
-
-            fs.DeleteThumbnails(path);
-        }
-
-        internal static void DeleteThumbnails(this MediaFileSystem fs, string path)
-        {
-            fs.GetThumbnails(path)
-                .ForEach(fs.DeleteFile);
-        }
-    }
-}
diff --git a/src/Umbraco.Core/IO/PhysicalFileSystem.cs b/src/Umbraco.Core/IO/PhysicalFileSystem.cs
index 4c7dd42f5e..a53b5b1784 100644
--- a/src/Umbraco.Core/IO/PhysicalFileSystem.cs
+++ b/src/Umbraco.Core/IO/PhysicalFileSystem.cs
@@ -4,9 +4,12 @@ using System.IO;
 using System.Linq;
 using System.Text;
 using System.Web;
+using Umbraco.Core.CodeAnnotations;
 
 namespace Umbraco.Core.IO
 {
+
+	[UmbracoExperimentalFeature("http://issues.umbraco.org/issue/U4-1156", "Will be declared public after 4.10")]
     internal class PhysicalFileSystem : IFileSystem
     {
         private readonly string _rootPath;
diff --git a/src/Umbraco.Core/Umbraco.Core.csproj b/src/Umbraco.Core/Umbraco.Core.csproj
index f9f56a3c81..d44959f632 100644
--- a/src/Umbraco.Core/Umbraco.Core.csproj
+++ b/src/Umbraco.Core/Umbraco.Core.csproj
@@ -81,7 +81,7 @@
     <Compile Include="Dynamics\ExtensionMethods.cs" />
     <Compile Include="Dynamics\PropertyResultType.cs" />
     <Compile Include="IO\FileSystemProviderAttribute.cs" />
-    <Compile Include="IO\IFileSystemExtensions.cs" />
+    <Compile Include="IO\FileSystemExtensions.cs" />
     <Compile Include="IO\MediaFileSystem.cs" />
     <Compile Include="Macros\MacroTagParser.cs" />
     <Compile Include="Mandate.cs" />
@@ -144,7 +144,6 @@
     <Compile Include="IO\FileSystemProviderManager.cs" />
     <Compile Include="IO\IFileSystem.cs" />
     <Compile Include="IO\IOHelper.cs" />
-    <Compile Include="IO\MediaFileSystemExtensions.cs" />
     <Compile Include="IO\PhysicalFileSystem.cs" />
     <Compile Include="IO\SystemDirectories.cs" />
     <Compile Include="IO\SystemFiles.cs" />