Inches matter! The Dead Foot Arms MCS buffer tube is the shortest AR-9 pistol tube currently available for the AR-9 platform. Compatible with most all AR-9's (Glock, Colt, Endomag and MP5/MP9 magazines) including the Angstadt Arms UDP-9 and 0940 receivers. The MCS stands for modified cycle system because Dead Foot Arms has shortened the buffer tube of a traditional AR-9 system from 7" to just 2.5". This is the shortest PCC pistol tube available. Form 1 SBR users: If you plan on converting your pistol to a SBR (short barrel rifle) or you're currently waiting on your ATF form 1 to be approved, this is the product to get. The pistol kit does not include the the folding stock adaptor. However, once you receive your approved form 1 you can add the MCS folding adaptor to this system by ordering a Pistol Kit to MCS Folder conversion kit. This is a complete short pistol tube kit including: Shortened pistol buffer tube and end cap assembly 9MM MCS Bolt Carrier Group with black nitride finish End plate with QD port Plunger, spring cap and recoil/plunger springs and rubber bumper for 9mm Shortened 9MM BCG - Materials & Features: Shortened 8620 steel single piece 9MM bolt with a Blacknitride+(TM) finish by H&M AR15 Style Extractor 17-4 Stainless Steel Firing Pin with Spring Functions with all AR-9 style PCC magazines including: Glock, Colt Style Magazine, Endomag and MP5/MP9 Fostech Echo Binary Cut Full Auto Compatible 100% American Made About the Company: Dead Foot Arms LLC designs, develops, assembles, and markets innovative firearm parts of the highest quality for demanding applications in the commercial, law enforcement, and defense markets. Their core value is to provide innovative cutting edge products to our customers through quality processes and continuous improvement initiatives. Dead Foot Arms LLC is a Veteran owned and Operated Small Business. And their products are and always will be proudly MADE IN THE USA.