diff --git a/Packages/com.teach310.core-bluetooth-for-unity/Runtime/SafeNativeATTRequestHandle.cs b/Packages/com.teach310.core-bluetooth-for-unity/Runtime/SafeNativeATTRequestHandle.cs
index 3c677d0..fb147db 100644
--- a/Packages/com.teach310.core-bluetooth-for-unity/Runtime/SafeNativeATTRequestHandle.cs
+++ b/Packages/com.teach310.core-bluetooth-for-unity/Runtime/SafeNativeATTRequestHandle.cs
@@ -3,7 +3,7 @@
 
 namespace CoreBluetooth
 {
-    public class SafeNativeATTRequestHandle : SafeHandle
+    internal class SafeNativeATTRequestHandle : SafeHandle
     {
         public override bool IsInvalid => handle == IntPtr.Zero;
 
diff --git a/Packages/com.teach310.core-bluetooth-for-unity/Runtime/SafeNativeATTRequestsHandle.cs b/Packages/com.teach310.core-bluetooth-for-unity/Runtime/SafeNativeATTRequestsHandle.cs
index de39d2b..f756558 100644
--- a/Packages/com.teach310.core-bluetooth-for-unity/Runtime/SafeNativeATTRequestsHandle.cs
+++ b/Packages/com.teach310.core-bluetooth-for-unity/Runtime/SafeNativeATTRequestsHandle.cs
@@ -3,7 +3,7 @@
 
 namespace CoreBluetooth
 {
-    public class SafeNativeATTRequestsHandle : SafeHandle
+    internal class SafeNativeATTRequestsHandle : SafeHandle
     {
         public override bool IsInvalid => handle == IntPtr.Zero;
 
diff --git a/Packages/com.teach310.core-bluetooth-for-unity/Runtime/SafeNativePeripheralManagerHandle.cs b/Packages/com.teach310.core-bluetooth-for-unity/Runtime/SafeNativePeripheralManagerHandle.cs
index 01bed52..b3737dd 100644
--- a/Packages/com.teach310.core-bluetooth-for-unity/Runtime/SafeNativePeripheralManagerHandle.cs
+++ b/Packages/com.teach310.core-bluetooth-for-unity/Runtime/SafeNativePeripheralManagerHandle.cs
@@ -3,7 +3,7 @@
 
 namespace CoreBluetooth
 {
-    public class SafeNativePeripheralManagerHandle : SafeHandleZeroOrMinusOneIsInvalid
+    internal class SafeNativePeripheralManagerHandle : SafeHandleZeroOrMinusOneIsInvalid
     {
         SafeNativePeripheralManagerHandle() : base(true) { }
 
diff --git a/Packages/com.teach310.core-bluetooth-for-unity/Runtime/StringExtensions.cs b/Packages/com.teach310.core-bluetooth-for-unity/Runtime/StringExtensions.cs
index 4963bf0..8c56838 100644
--- a/Packages/com.teach310.core-bluetooth-for-unity/Runtime/StringExtensions.cs
+++ b/Packages/com.teach310.core-bluetooth-for-unity/Runtime/StringExtensions.cs
@@ -2,7 +2,7 @@
 
 namespace CoreBluetooth
 {
-    public static class StringExtensions
+    internal static class StringExtensions
     {
         private static readonly Regex CBUUIDRegex = new Regex(@"^([0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}|[0-9a-f]{8}|[0-9a-f]{4})$", RegexOptions.IgnoreCase);