Every good scope needs a good foundation, that's why you want to use Optilock bases on your next mounting project. Optilock bases are precisely machined out of solid steel to ensure perfect mating with our integral receiver scope mount rails and optimal scope alignment. Optilock scope mount bases come clamshell packed in pairs will all the parts required for assembling bases to the receiver of your firearm. The size of base that you need can be determined by the caliber of your rifle and corresponding action type.