Tacmod US Tactical Systems Back-Up 20 and A2 Buttstock Installation Kit Black. This kit includes everything needed. Back-Up 20 Stock & A2 Installation Kit Installs on any AR-15 or M16 lower receiver to accept the A2 style Back-Up 20 Stock. This kit includes everything needed to get your Back-Up 20 installed in minutes. Includes Buffer Buffer Tube Spring Stock Extension Cap and hardware. This kit is a standard size so it will work on other AR-15 and M16 A2 stock installations as well. If you plan on purchasing the US Tactical Systems Back-Up 20 Stock and this kit please see item 660-754. Save money by purchasing together Specifications for Tacmod US Tactical Systems Back-Up 20 and A2 Buttstock Installation Kit: Manufacturer: Tacmod Color: Black Finish: Matte Fabric/Material: Steel Gun Make: AR Platform Condition: New Package Contents: Tacmod US Tactical Systems Back-Up 20 and A2 Buttstock Installation Kit Tacmod 660-753: US Tactical Systems Back-Up 20 and A2 Buttstock Installation Kit Black