This drum magazine has housing constructed of proprietary DuPont Zytel based polymer. The magazine?s upper tower has a full length steel insert that is stamped and welded like the factory magazine. Additional components include an injection molded magazine follower and a spring formed from heat treated stainless steel.Features:Fits Glock 42;Drum housing constructed of proprietary DuPont Zytel based polymer;Magazine upper tower has full length steel internal insert stamped and welded like the factory magazine;Injection molded magazine follower;Magazine spring formed from heat treated stainless steel