To ensure reliable function, this magazine has the same polymer and steel construction as factory mags, including a heat-treat hardened chrome silicon spring, and a smooth polymer follower that keeps the round stack moving. Polymer body with reinforcing internal steel tube Removable baseplate Witness holes to keep you apprised of round count Compatible with any accessories that fit Glock factory magazines Built exactly good-as-factory specs, the KCI 15-round magazine will keep the rounds cycling smoothly and reliably through your Glock 19 or 26 - or your "AR-9" carbine, pistol, or SBR.