This is a Phase 5 Weapon Systems Magazine Release known as the PMR, model PMR-BLK.
The Phase 5 PMR is a CNC machined 6061-T6 billet aluminum magazine release button. Easy to install" the PMR is a drop in component that replaces the Mil-Spec magazine release button. Including a textured angle serration design on the button face" the PMR adds style and keeps the function of a Mil-Spec button.
Features:
Fits AR 5.56/.223 and 7.62/.308 Receivers
6061-T6 Billet Aluminum
Anodized Finish