diff --git a/aiocraft/mc/types.py b/aiocraft/mc/types.py
index b1c0f0d..f6ffe71 100644
--- a/aiocraft/mc/types.py
+++ b/aiocraft/mc/types.py
@@ -3,8 +3,12 @@ import struct
 import asyncio
 import uuid
 
+import logging
+import pynbt
+
 from typing import List, Tuple, Dict, Any, Union, Optional, Type as Class
 
+
 class Type(object):
 	pytype : type
 
@@ -44,8 +48,6 @@ class UnimplementedDataType(Type):
 TrailingData = UnimplementedDataType()
 EntityMetadata = UnimplementedDataType()
 EntityMetadataItem = UnimplementedDataType()
-NBTTag = UnimplementedDataType()
-Slot = UnimplementedDataType()
 
 class PrimitiveType(Type):
 	size : int
@@ -75,6 +77,21 @@ Float = PrimitiveType(float, ">f", 4)
 Double = PrimitiveType(float, ">d", 8)
 Angle = PrimitiveType(int, ">b", 1)
 
+class NBTType(Type):
+
+	def write(self, data:pynbt.NBTFile, buffer:io.BytesIO, ctx:object=None):
+		data.save(buffer)
+
+	def read(self, buffer:io.BytesIO, ctx:object=None) -> Optional[pynbt.NBTFile]:
+		head = Byte.read(buffer)
+		if head == 0x0:
+			return None
+		buffer.seek(-1,1) # go back 1 byte
+		return pynbt.NBTFile(io=buffer)
+
+NBTTag = NBTType()
+# NBTTag = TrailingData
+
 class VarLenPrimitive(Type):
 	pytype : type = int
 	max_bytes : int
@@ -159,6 +176,13 @@ class BufferType(Type):
 ByteArray = BufferType()
 IntegerByteArray = BufferType(Int)
 
+def twos_comp(val, bits):
+	"""compute the 2's complement of int value val"""
+	if (val & (1 << (bits - 1))) != 0: # if sign bit is set e.g., 8bit: 128-255
+		val = val - (1 << bits)        # compute negative value
+	return val                         # return positive value as is
+
+
 class PositionType(Type):
 	pytype : type = tuple
 	MAX_SIZE : int = 8
@@ -166,14 +190,16 @@ class PositionType(Type):
 	# TODO THIS IS FOR 1.12.2!!! Make a generic version-less?
 
 	def write(self, data:tuple, buffer:io.BytesIO, ctx:object=None):
-		packed = ((0x3FFFFFF & data[0]) << 38) | ((0xFFF & data[1]) << 26) | (0x3FFFFFF & data[2])
+		packed = ((0x3FFFFFF & data[0]) << 38) \
+			| ((0xFFF & data[1]) << 12) \
+			| (0x3FFFFFF & data[2])
 		UnsignedLong.write(packed, buffer, ctx=ctx)
 
 	def read(self, buffer:io.BytesIO, ctx:object=None) -> tuple:
 		packed = UnsignedLong.read(buffer)
-		x = packed >> 38
-		y = (packed >> 24) & 0xFFF
-		z = packed & 0x3FFFFFF
+		x = twos_comp(packed >> 38, 26)
+		y = (packed >> 26) & 0xFFF
+		z = twos_comp(packed & 0x3FFFFFF, 26)
 		return (x, y, z)
 
 Position = PositionType()
@@ -209,7 +235,10 @@ class ArrayType(Type):
 
 	def read(self, buffer:io.BytesIO, ctx:object=None) -> List[Any]:
 		length = self.counter if isinstance(self.counter, int) else self.counter.read(buffer, ctx=ctx)
-		return [ self.content.read(buffer, ctx=ctx) for _ in range(length) ]
+		out = []
+		for _ in range(length):
+			out.append(self.content.read(buffer, ctx=ctx))
+		return out
 
 class OptionalType(Type):
 	t : Type
@@ -238,15 +267,15 @@ class SwitchType(Type):
 		self.default = default
 
 	def write(self, data:Any, buffer:io.BytesIO, ctx:object=None):
-		watched = getattr(ctx, self.field)
-		if watched in self.mappings:
+		watched = getattr(ctx, self.field, None)
+		if watched is not None and watched in self.mappings:
 			return self.mappings[watched].write(data, buffer, ctx=ctx)
 		elif self.default:
 			return self.default.write(data, buffer, ctx=ctx)
 
 	def read(self, buffer:io.BytesIO, ctx:object=None) -> Optional[Any]:
-		watched = getattr(ctx, self.field)
-		if watched in self.mappings:
+		watched = getattr(ctx, self.field, None)
+		if watched is not None and watched in self.mappings:
 			return self.mappings[watched].read(buffer, ctx=ctx)
 		elif self.default:
 			return self.default.read(buffer, ctx=ctx)
@@ -265,5 +294,41 @@ class StructType(Type):
 
 	def read(self, buffer:io.BytesIO, ctx:object=None) -> Dict[str, Any]:
 		return { k : t.read(buffer, ctx=ctx) for k, t in self.fields }
+	
+class SlotType(Type):
+	pytype : type = dict
+
+	def write(self, data:Any, buffer:io.BytesIO, ctx:object=None):
+		new_way = ctx._proto > 340
+		check_type = Boolean if new_way else Short
+		if data:
+			check_type.write(True if new_way else data["id"], buffer)
+			if new_way:
+				VarInt.write(data["id"], buffer)
+			Byte.write(data["count"], buffer)
+			if not new_way:
+				Short.write(data["damage"], buffer)
+			NBTTag.write(data["nbt"], buffer)
+		else:
+			check_type.write(False if new_way else -1, buffer)
+
+	def read(self, buffer:io.BytesIO, ctx:object=None) -> Any:
+		slot = {}
+		new_way = ctx._proto > 340
+		check_type = Boolean if new_way else Short
+		val = check_type.read(buffer)
+		if (new_way and val) or val != -1:
+			if new_way:
+				slot["id"] = VarInt.read(buffer)
+			else:
+				slot["id"] = val
+			slot["count"] = Byte.read(buffer)
+			if not new_way:
+				slot["damage"] = Short.read(buffer)
+			slot["nbt"] = NBTTag.read(buffer)
+		return slot
+
+Slot = SlotType()
+# Slot = TrailingData
 
 
diff --git a/requirements.txt b/requirements.txt
index 6787c69..9dc0c11 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -1,3 +1,4 @@
+pynbt
 cryptography
 aiohttp
 termcolor