Tacmod US Tactical Systems Back-Up 20 AR Stock Black. This gun stock manufactured by the experts at Tacmod is constructed of durable Dupont Zytel replaces the standard M16A2 or AR-15 buttstock and maintains the weapons existing handling characteristics. The US Tactical Systems Back-Up 20 AR Buttstock w/ Push Button retains the spare magazine using the same latching mechanism as the regular M16A2. The magazine is securely stored in a dust-free environment until the trap door is deliberately opened and the magazine release button is pushed. The US Tactical Systems Back-Up 20 AR Stock will only add minimal bulk to the overall weapon yet the extra magazine may be the difference between life and death. Specifications for Tacmod US Tactical Systems Back-Up 20 AR Stock: Manufacturer: Tacmod Color: Black Stock/Brace Material: Steel Gun Model: AR-15 Gun Make: AR Platform Gun Type: Rifle Fabric/Material: Steel Finish: Matte Black Package Contents: Tacmod US Tactical Systems Back-Up 20 AR Stock What firearm models does the manufacturer say Tacmod US Tactical Systems Back-Up 20 AR Stock is compatible with? The manufacturer says that Tacmod US Tactical Systems Back-Up 20 AR Stock is compatible with AR-15Tacmod 660-752: US Tactical Systems Back-Up 20 AR Stock Black