The S15 magazine is a patent-pending, flush-fitting 15 round magazine for the GlockA(R) 43X and GlockA(R) 48. The S15 is a steel magazine, and is the same length as the OEM GlockA(R) 10 round magazine, but holds an additional 5 rounds. Increased Capacity, Same Reliability What changed with the gen 3 magazine? We made the following improvements: New US-based manufacturer Modular tooling, allowing us to make the S15 and S10 magazines simultaneously Raised ribs on the back of the magazine allows us to fully match the OEM magazine position in the mag well, which should eliminate any tolerance stacking that results from Glock frame variations New steel, n Mfg: Shield Arms