This 17-round magazine from ProMag is compatible with Glock G21 and Glock G30 45 ACP pistols.The magazine body is constructed of a proprietary DuPont Zytel-based polymer with a full-length steel internal insert stamped and welded just like the factory magazine.In addition it has a spring made from heat-treated chrome silicon wire and an injection-molded magazine follower for consistent and reliable feeding.ProMag Glock G21/G30 45 ACP Magazine17 Round CapacityCompatible With Glock G21 and Glock G30 45 ACP PistolsOrder your ProMag Glock G21/G30 magazine online today!Score big savings and fast shipping when you shop our large selection of cheap bulk .45 ACP ammo for sale.