Stern Defense 008SDRABADD1M Rapid Attach Buttstock Adapter Black Aluminum/Steel

"How to use:  To detach, push the button and twist counter-clockwise 30 degrees.The buttstock will then be separated from the firearm. To re-attach, align the two pieces, push in and turn clockwise 30 degrees. The steel locking mechanism automatically secures the adapter. It's 7075 aluminum construction and steel internals make the RAB-AD both robust and lightweight. The RAB-AD is designed for gas piston, direct impingement, direct blow back and radial delayed blowback systems in the AR platform.    RAB-AD Features  Designed, machined, and assembled in the U.S.A 7075 aluminum body Steel internals Hard coat anodized for maximum wear protection Buffer retainer to keep the buffer weight in the tube while disassembled Buffer spacer compatible with all standard-length AR-15 bolts RAB-AD weighs 3.5ounces Adds 1.25 inches to length of pull   NOTE: The RAB-AD is not compatible with BCG's that have a flared boss at the tail of the carrier. The tail of the BCG must be .950"" or smaller. Is compatible with the JP silent capture spring. "