The SBT5 enhances your MP5/MP5K Reverse Stretch with an integral, side-folding polymer endplate. FITS: HK SP5, CENTURY ARMS AP5, ZENITH ZF-5, PTR 9CT, MOST MP5 CLONES (9MM ONLY) FEATURES Complete assembly, ready-to-install Molded polymer end cap with QD socket Integral, side-folding mechanism Designed for 9mm only US veteran designed and proudly made in the USA Due to varying tolerances between roller lock manufacturers, gunsmith installation / fitting may be required.