First Generation Buffer Tube (Receiver Extension) for Colt sliding stock models: XM177, XM177E2 and Colt Commando Models up to the 1980's.
Original Colt variants were first 2 position - just like this one.
In the 80's it was replaced by the 4 position
Most current builds now use a 6 position
- 2 Position Mil-Spec size (Made in USA)
- 4 Position Mil-Spec size (Genuine NOS Part) (Made in USA)
- 4 position Commercial Size (Made in USA)
- 6 Position Mil-Spec Size (unknown origin)