Sniper Commercial Spec 6 Position Aluminum Receiver Extension Tube and Buffer Kit Black. 223. The buffer tube screws into the upper and is held into place with the castle locking nut and receiver plate. Specifications for Sniper Commercial Spec 6 Position Aluminum Receiver Extension Tube and Buffer Kit: Manufacturer: Sniper Color: Black Finish: Matte Anodizing with Type III Class II Hard Coat Fabric/Material: Aircraft Grade Aluminum Gun Make: AR Platform Gun Model: AR-15 Condition: New Caliber: 5.56x45mm NATO .223 Remington Package Contents: Sniper Commercial Spec 6 Position Aluminum Receiver Extension Tube and Buffer Kit What firearm models does the manufacturer say Sniper Commercial Spec 6 Position Aluminum Receiver Extension Tube and Buffer Kit is compatible with? The manufacturer suggests that Sniper Commercial Spec 6 Position Aluminum Receiver Extension Tube and Buffer Kit is compatible with AR-15Sniper AS5P01: Sniper Commercial Spec 6 Position Aluminum Receiver Extension Tube and Buffer Kit Black