diff --git a/Recyclable.Collections/RecyclableList.Enumerator.cs b/Recyclable.Collections/RecyclableList.Enumerator.cs
index 89a9be0..7dc6adc 100644
--- a/Recyclable.Collections/RecyclableList.Enumerator.cs
+++ b/Recyclable.Collections/RecyclableList.Enumerator.cs
@@ -1,87 +1,185 @@
 using System.Collections;
 using System.Diagnostics.Contracts;
 using System.Runtime.CompilerServices;
-using System.Runtime.ConstrainedExecution;
+using System.Runtime.InteropServices;
 
 namespace Recyclable.Collections
 {
 	public partial class RecyclableList<T>
 	{
-
-		public struct Enumerator : IEnumerator<T>, IEnumerator
+		[StructLayout(LayoutKind.Auto)]
+		public struct Enumerator : IEnumerator<T>
 		{
-#nullable disable
-			private readonly RecyclableList<T> _list;
 			private int _currentIndex;
-			private T _current;
+			private readonly ulong _enumeratorVersion;
+			private readonly RecyclableList<T> _list;
 
-			//[Pure]
-			//private readonly int _listCount;
-			//private readonly int _listCountMinus1;
-			//private readonly T[] _memoryBlock;
-			//private bool _endOfCollectionReached;
+			// & WAS SLOWER
+			// private bool _isInValidState = false;
+			// private bool _endOfCollectionReached;
+			// private T _current;
 
-			//private RecyclableCollectionVersion _listVersion;
-			//private ulong _enumeratorVersion;
-			//private bool _isVersionChanged;
-
-			//private void VersionChanged() => _isVersionChanged = true;
-
-			//internal RecyclableListEnumeratorPool? _pool;
-			//internal bool _returned;
-
-			//public RecyclableListEnumerator()
-			//{
-			//}
-
-			//[Pure]
-			internal Enumerator(RecyclableList<T> list)
+#nullable disable
+			// [Pure]
+			public readonly T Current
 			{
-				_current = default;
-				_currentIndex = 0;
-				_list = list;
-				//_memoryBlock = list._memoryBlock;
-				//_listCount = list._count;
-				//_listVersion = list._version!;
-				//_listVersion.VersionChanged += VersionChanged;
-				//_enumeratorVersion = _listVersion.Version;
+				get
+				{
+					if (_enumeratorVersion != _list._version)
+					{
+						throw new InvalidOperationException();
+						// & WAS SLOWER
+						// ThrowHelper.ThrowListModifiedException();
+					}
+
+					if (_currentIndex == 0 || _currentIndex > _list._count)
+					{
+						throw new IndexOutOfRangeException();
+						// & WAS SLOWER
+						// ThrowHelper.ThrowCollectionNotInitialized();// new IndexOutOfRangeException();// _current;
+					}
+
+					Contract.EndContractBlock();
+
+					return _list._memoryBlock[_currentIndex - 1];// _current;
+				}
 			}
 
-			//{
-			//	//[MethodImpl(MethodImplOptions.AggressiveInlining)]
-			//	get =>
-			//			//if (_currentIndex < 0)
-			//			//{
-			//			//	ThrowHelper.ThrowInvalidOperationException("The enumerator wasn't initialized. You need to call MoveNext() before getting the current iterator value");
-			//			//}
-			//			//else
-			//			//if (_endOfCollectionReached)
-			//			//{
-			//			//	throw new InvalidOperationException("The enumerator reached the end of the collection. You need to call Reset(), if you want to enumerate the collection again");
-			//			//}
-			//			//else
-			//			//{
-			//			//if (_currentIndex < 0)
-			//			//{
-			//			//	ThrowHelper.ThrowInvalidOperationException("The enumerator wasn't initialized. You need to call MoveNext() before getting the current iterator value");
-			//			//}
-			//			//else
-			//			_memoryBlock[_currentIndex];//}
-			//}
+			// [Pure]
+			object IEnumerator.Current
+			{
+				get
+				{
+					if (_enumeratorVersion != _list._version)
+					{
+						throw new InvalidOperationException();
+						// & WAS SLOWER
+						// ThrowHelper.ThrowListModifiedException();
+					}
+
+					if (_currentIndex == 0 || _currentIndex > _list._count)
+					{
+						throw new IndexOutOfRangeException();
+						// & WAS SLOWER
+						// ThrowHelper.ThrowCollectionNotInitialized();
+					}
+
+					Contract.EndContractBlock();
+
+					return _list._memoryBlock[_currentIndex - 1];
+
+					// & WAS SLOWER
+					// return _current;
+				}
+			}
+
+			// & WAS SLOWER
+			// private readonly int _listCount;
+			// private RecyclableCollectionVersion _listVersion;
+			// private readonly T[] _memoryBlock;
+			// private bool _isVersionChanged;
+			// private void VersionChanged() => _isVersionChanged = true;
+			// internal RecyclableListEnumeratorPool? _pool;
+			// internal bool _returned;
+			// private readonly int _listCountMinus1;
+
+			// & WAS SLOWER
+			// [MethodImpl(MethodImplOptions.AggressiveInlining)]
+			// [MethodImpl(MethodImplOptions.NoInlining)]
+			public bool MoveNext()
+			{
+				// & WAS SLOWER
+				// var list = _list;
+				if (_enumeratorVersion != _list._version)
+				{
+					throw new InvalidOperationException();
+					// & WAS SLOWER
+					// ThrowHelper.ThrowListModifiedException();
+				}
+
+				Contract.EndContractBlock();
+
+				// & WAS SLOWER
+				// if (_currentIndex == 0)
+				// {
+				// 	_isInValidState = true;
+				// 	_currentIndex++;
+				// 	return true;
+				// }
+				// else
+				if (_currentIndex < _list._count)
+				{
+					// & WAS SLOWER
+					// _current = _list._memoryBlock[_currentIndex];
+					_currentIndex++;
+					return true;
+				}
+
+				// & WAS SLOWER
+				// else if (_currentIndex == _list._count)
+				// {
+					// & WAS SLOWER
+					// This isn't needed in most use-cases, because the enumerator will get disposed, releasing the reference, if any.
+					// _current = _defaultValue;
+				// _currentIndex++;
+				// 	return false;
+				// }
+				// else if (!_endOfCollectionReached)
+				// {
+				// 	// & WAS SLOWER
+				// 	// This isn't needed in most use-cases, because the enumerator will get disposed, releasing the reference, if any.
+				// 	// _current = _defaultValue;
+				// 	// _currentIndex = int.MinValue;
+				// 	_endOfCollectionReached = true;
+				// 	return false;
+				// }
+
+				// & WAS SLOWER
+				// else if (!_endOfCollectionReached)
+				// {
+				// 	_current = default;
+				// 	_endOfCollectionReached = true;
+				// 	return false;
+				// }
+
+				// & WAS SLOWER
+				// _current = default;
+				// _currentIndex = _list._count + 1;
+				return false;
+			}
+
+			public Enumerator(RecyclableList<T> list)
+			{
+				_currentIndex = 0;
+				_list = list;
+				_enumeratorVersion = list._version;
+
+				// & WAS SLOWER
+				// _current = default;
+				// _endOfCollectionReached = false;
+				// _listCount = list._count;
+				// _memoryBlock = list._memoryBlock;
+				// _isVersionChanged = false;
+				// _listVersion = list.Version;
+				// _listVersion.AddEnumerator();
+				// _enumeratorVersion = list._version.Version;
+				// list._version.RegisterHandler(VersionChanged);
+				// _enumeratorVersion = _listVersion.Version;
+				// _endOfCollectionReached = false;
+				// _listCountMinus1 = list._count - 1;
+			}
 
-			//[Pure]
 			public readonly void Dispose()
 			{
-				//				if (_listVersion != null)
-				//				{
-				//					_listVersion.VersionChanged -= VersionChanged;
-				//					//_listVersion.RemoveEnumerator(this);
-				//#nullable disable
-				//					_listVersion = null;
-				//#nullable restore
-				//				}
+				// & WAS SLOWER
+				//if (_listVersion != null)
+				//{
+					//_list._version.RemoveEnumerator();
+					//_listVersion.RemoveEnumerator(this);
+				//}
 
-				//if (_pool != null)
+				// & WAS SLOWER
+				// if (_pool != null)
 				//{
 				//	if (!_returned)
 				//	{
@@ -92,74 +190,19 @@ namespace Recyclable.Collections
 				//else
 				//{
 				//_memoryBlock = null;
-					//GC.SuppressFinalize(this);
+				//GC.SuppressFinalize(this);
 				//}
 			}
 
-			//[MethodImpl(MethodImplOptions.AggressiveInlining)]
-			public bool MoveNext()
-			{
-				var list = _list;
-				//if (_isVersionChanged)
-				//{
-				//	ThrowHelper.ThrowListModifiedException();
-				//	return false;
-				//}
-				//else
-				if (_currentIndex < list._count)
-				{
-					_current = list._memoryBlock[_currentIndex];
-					_currentIndex++;
-					return true;
-				}
-
-				//else if (!_endOfCollectionReached)
-				//{
-				//	_endOfCollectionReached = true;
-				//	return false;
-				//}
-
-				_current = default;
-				return false;
-			}
-
-#nullable restore
-			public T Current => _current;
-			object IEnumerator.Current => _current;
-#nullable disable
-
-			//[MethodImpl(MethodImplOptions.AggressiveInlining)]
 			void IEnumerator.Reset()
 			{
 				_currentIndex = 0;
-				_current = default;
+
+				// & WAS SLOWER
+				// _endOfCollectionReached = false;
+				// _isInValidState = false;
+				// _current = default;
 			}
-
-			//_endOfCollectionReached = false;
-			//if (_isVersionChanged)
-			//{
-			//	
-			//_enumeratorVersion = _listVersion!.Version;
-			//	_isVersionChanged = false;
-			//}
-
-			//internal RecyclableListEnumerator Reset(RecyclableListEnumeratorPool pool, RecyclableList<T> list)
-			//{
-			//	_returned = false;
-			//	if (_pool != pool)
-			//	{
-			//		_pool = pool;
-			//	}
-
-			//	_currentIndex = RecyclableDefaults.ItemNotFoundIndex;
-			//	_listVersion = list._version!;
-			//	_enumeratorVersion = _listVersion!.Version;
-			//	list._version!.AddEnumerator();
-			//	return this;
-			//}
-
-			//[Pure]
-			//public object Clone() => MemberwiseClone();
 		}
 	}
 #nullable restore
diff --git a/Recyclable.Collections/RecyclableList.cs b/Recyclable.Collections/RecyclableList.cs
index e823ef4..6e1518f 100644
--- a/Recyclable.Collections/RecyclableList.cs
+++ b/Recyclable.Collections/RecyclableList.cs
@@ -15,9 +15,12 @@ namespace Recyclable.Collections
 		public static explicit operator ReadOnlySpan<T>(RecyclableList<T> source) => new(source._memoryBlock, 0, source.Count);
 
 		protected T[] _memoryBlock;
-		internal RecyclableCollectionVersion? _version;
+		// & WAS SLOWER
+		// internal RecyclableCollectionVersion _version;
+		// public RecyclableCollectionVersion Version => _version;
 
-		public RecyclableCollectionVersion? Version => _version;
+		protected ulong _version;
+		public ulong Version => _version;
 
 		protected IEnumerator<T> AddRangeEnumerated(IEnumerable<T> source, int growByCount)
 		{
@@ -196,11 +199,7 @@ namespace Recyclable.Collections
 			set
 			{
 				_memoryBlock[index] = value;
-
-				if (_version?.IsVersioned ?? false)
-				{
-					_version.Inc();
-				}
+				_version++;
 			}
 		}
 
@@ -214,11 +213,7 @@ namespace Recyclable.Collections
 				{
 					_memoryBlock = Resize(_memoryBlock, value);
 					_capacity = _memoryBlock.Length;
-				}
-
-				if (_version?.IsVersioned ?? false)
-				{
-					_version.Inc();
+					_version++;
 				}
 			}
 		}
@@ -254,11 +249,7 @@ namespace Recyclable.Collections
 			}
 
 			_memoryBlock[_count++] = item;
-
-			if (_version?.IsVersioned ?? false)
-			{
-				_version.Inc();
-			}
+			_version++;
 		}
 
 		[MethodImpl(MethodImplOptions.NoInlining | MethodImplOptions.AggressiveOptimization)]
@@ -281,10 +272,7 @@ namespace Recyclable.Collections
 			itemsSpan.CopyTo(targetSpan);
 			_count = targetCapacity;
 
-			if (_version?.IsVersioned ?? false)
-			{
-				_version.Inc();
-			}
+			_version++;
 		}
 
 		[MethodImpl(MethodImplOptions.NoInlining | MethodImplOptions.AggressiveOptimization)]
@@ -306,10 +294,7 @@ namespace Recyclable.Collections
 			itemsSpan.CopyTo(targetSpan);
 			_count = targetCapacity;
 
-			if (_version?.IsVersioned ?? false)
-			{
-				_version.Inc();
-			}
+			_version++;
 		}
 
 		[MethodImpl(MethodImplOptions.NoInlining | MethodImplOptions.AggressiveOptimization)]
@@ -330,10 +315,7 @@ namespace Recyclable.Collections
 			items.CopyTo(_memoryBlock, _count);
 			_count = targetCapacity;
 
-			if (_version?.IsVersioned ?? false)
-			{
-				_version.Inc();
-			}
+			_version++;
 		}
 
 		[MethodImpl(MethodImplOptions.NoInlining | MethodImplOptions.AggressiveOptimization)]
@@ -354,10 +336,7 @@ namespace Recyclable.Collections
 			items.CopyTo(_memoryBlock, _count);
 			_count = targetCapacity;
 
-			if (_version?.IsVersioned ?? false)
-			{
-				_version.Inc();
-			}
+			_version++;
 		}
 
 		[MethodImpl(MethodImplOptions.NoInlining | MethodImplOptions.AggressiveOptimization)]
@@ -380,10 +359,7 @@ namespace Recyclable.Collections
 			itemsSpan.CopyTo(targetSpan);
 			_count = targetCapacity;
 
-			if (_version?.IsVersioned ?? false)
-			{
-				_version.Inc();
-			}
+			_version++;
 		}
 
 		[MethodImpl(MethodImplOptions.NoInlining | MethodImplOptions.AggressiveOptimization)]
@@ -438,10 +414,7 @@ namespace Recyclable.Collections
 
 			_count = targetCapacity;
 
-			if (_version?.IsVersioned ?? false)
-			{
-				_version.Inc();
-			}
+			_version++;
 		}
 
 		[MethodImpl(MethodImplOptions.NoInlining | MethodImplOptions.AggressiveOptimization)]
@@ -467,19 +440,13 @@ namespace Recyclable.Collections
 			{
 				AddRangeWithKnownCount(source, _count, requiredAdditionalCapacity);
 
-				if (_version?.IsVersioned ?? false)
-				{
-					_version.Inc();
-				}
+				_version++;
 			}
 			else
 			{
 				AddRangeEnumerated(source, growByCount);
 
-				if (_version?.IsVersioned ?? false)
-				{
-					_version.Inc();
-				}
+				_version++;
 			}
 		}
 
@@ -494,11 +461,7 @@ namespace Recyclable.Collections
 			}
 
 			_count = 0;
-
-			if (_version?.IsVersioned ?? false)
-			{
-				_version.Inc();
-			}
+			_version++;
 		}
 
 		[MethodImpl(MethodImplOptions.AggressiveInlining)]
@@ -529,11 +492,7 @@ namespace Recyclable.Collections
 
 			_memoryBlock[index] = item;
 			_count++;
-
-			if (_version?.IsVersioned ?? false)
-			{
-				_version.Inc();
-			}
+			_version++;
 		}
 
 		[MethodImpl(MethodImplOptions.AggressiveInlining | MethodImplOptions.AggressiveOptimization)]
@@ -555,10 +514,7 @@ namespace Recyclable.Collections
 #pragma warning restore CS8601
 				}
 
-				if (_version?.IsVersioned ?? false)
-				{
-					_version.Inc();
-				}
+				_version++;
 
 				return true;
 			}
@@ -587,22 +543,17 @@ namespace Recyclable.Collections
 #pragma warning restore CS8601
 			}
 
-			if (_version?.IsVersioned ?? false)
-			{
-				_version.Inc();
-			}
+			_version++;
 		}
 
+		[MethodImpl(MethodImplOptions.AggressiveInlining)]
 		public Enumerator GetEnumerator() => new Enumerator(this);
-		//[MethodImpl(MethodImplOptions.AggressiveInlining)]
-		IEnumerator IEnumerable.GetEnumerator() =>
-			//_version ??= new(); // RecyclableCollectionVersionPool.Shared.Get();
-			new Enumerator(this);//return RecyclableListEnumeratorPool.Shared.Get(this);
 
-		//[MethodImpl(MethodImplOptions.AggressiveInlining)]
-		IEnumerator<T> IEnumerable<T>.GetEnumerator() =>
-			//_version ??= new(); // RecyclableCollectionVersionPool.Shared.Get();
-			new Enumerator(this);//return RecyclableListEnumeratorPool.Shared.Get(this);
+		[MethodImpl(MethodImplOptions.AggressiveInlining)]
+		IEnumerator IEnumerable.GetEnumerator() => new Enumerator(this);
+
+		[MethodImpl(MethodImplOptions.AggressiveInlining)]
+		IEnumerator<T> IEnumerable<T>.GetEnumerator() => new Enumerator(this);
 
 		public void Dispose()
 		{
@@ -615,13 +566,6 @@ namespace Recyclable.Collections
 					_arrayPool.Return(_memoryBlock, NeedsClearing);
 				}
 
-				if (_version != null)
-				{
-					//var toReturn = _version;
-					_version = null;
-					//RecyclableCollectionVersionPool.Shared.Return(toReturn);
-				}
-
 				GC.SuppressFinalize(this);
 			}
 		}
diff --git a/Recyclable.CollectionsTests/RecyclableListTests.cs b/Recyclable.CollectionsTests/RecyclableListTests.cs
index b5a4dba..d47ca01 100644
--- a/Recyclable.CollectionsTests/RecyclableListTests.cs
+++ b/Recyclable.CollectionsTests/RecyclableListTests.cs
@@ -349,7 +349,11 @@ namespace Recyclable.CollectionsTests
 
 			// Act
 			var yieldedItems = new List<long>((int)itemsCount);
-			yieldedItems.AddRange(list);
+			using var enumerator = list.GetEnumerator();
+			while (enumerator.MoveNext())
+			{
+				yieldedItems.Add(enumerator.Current);
+			}
 
 			// Validate
 			_ = yieldedItems.Count.Should().Be((int)itemsCount);