STD rings are precision engineered to match up with STD 1-piece or STD 2-piece bases. Rear ring is secured by windage adjustment screws. High ring height, machined steel construction Product Specifications Strike-Forged Steel 28% strength improvement Anti-Slip Grooves No lapping required CNC Machined For perfect alignment Locking Screws with Nylok Won't back out under recoil or vibration