Strike Industries Picatinny Stock Adapter, Fits AR Rifles, Black SI-AR-PSA-BK The Strike AR Picatinny Stock Adapter gives the user the ability to mount a 1913 Picatinny interface stock/stabilizer assembly where normally the receiver extension is attached. For ARs that do not need an in-line buffer and buffer spring to function, this is a simple, fast and budget friendly conversion that works on both AR-15 and AR-10 lower receivers.