CAM-LOK (Covert Application Mount - Locking) Patented Universal QD piston attachment system; 3 mounting positions, 120 degrees separated for rapid mounting; Forward taper surface locks in place with interfacing piston and drastically reduces or eliminates common baffle/end cap strikes; Coarse threads are top cut to increase durability and wear resistance; 3/4" or 19mm wrench pattern accommodates socket wrench for secure and easy installation; Compatible with Universal QD pistons (sold separately); Internal bore reduces side concussion and visual disturbance vs blind muzzle; Total system weight is identical to legacy direct thread pistons; QPQ Nitride finish for attractive, durable black finish; 17-4 stainless steel material