Complete Assembly, Ready-To-Install Molded Polymer End Cap With QD Socket Integral, Side-Folding Mechanism Due To Varying Tolerances Between Roller Lock Manufacturers, Gunsmith Installation / Fitting May Be Required The SBT5K Enhances Your MP5K With An Integral, Side-Folding, Molded Polymer End Cap. FITS: 2 PIN K* MODELS SUCH AS HK SP89, HK SP5K, PTR 9KT, CENTURY ARMS AP5-P & AP5-M, MOST SP5K CLONES (9MM ONLY).