JE Machine Tech AR15 Receiver Extension Pistol Buffer Tube Combo Kit w/o Foam Black PS-BTP COMBO-NF. Our AR15 Pistol Buffer Tubes are machined from high strength 6061 T6 grade aluminum in a Mil-Spec diameter. Specifications for JE Machine Tech AR15 Receiver Extension No Foam Pistol Buffer Tube Combo Kit: Manufacturer: JE Machine Tech Color: Black Condition: New Features of JE Machine Tech AR15 Receiver Extension No Foam Pistol Buffer Tube Combo Kit Carbine Buffer Tube with Padding Mil-Spec carbine action spring Castle nut Standard end plate Package Contents: JE Machine Tech AR15 Receiver Extension No Foam Pistol Buffer Tube Combo Kit JE Machine Tech PS-BTP COMBO-NF: AR15 Receiver Extension Pistol Buffer Tube Combo Kit w/o Foam Black