Maxim Defense Industries Gen 7 CWB Pistol System, Standard Kit, Buffer Tube Complete Assembly, Anodized Finish, Black, Includes - Housing, Tube, Standard Buffer, Spring MXM-48531 The Gen 7 CQB Pistol System by Maxim Defense is your choice for simplicity and compactness for your AR-15 pistol. This system features a Gen 7 style housing" and CQB length buffer tube. It is compatible with your standard bolt carrier group" but you will need the proprietary CQB buffer & springs or JP Silent Captured Spring if you don't have one. The CQB Pistol System is compatible with any MIL-SPEC lower receiver and it does not accept a stabilizing brace. For those that are looking to convert their existing CQB system into the Pistol System" you only need the housing as your existing extension tube is compatible.