This replacement part is a factory original from GLOCK. Factory replacement parts are manufactured to the exact same specifications and tolerances resulting in excellent fit and reliable operation. Some parts may need to be installed by a qualified gunsmith. This GLOCK OEM 10 coil magazine spring fits models G17, G17L, G18, G20, G21, G22, G23, G24, G25, G28, G29, G30, G31, G32, G33, G34, G35 (including Gen4). G17, G18, G34: all 17-rd mags, incl. pre-ban, LE-marked & current unmarked (std 10-coil spring). G20: for all 15-rd mags, incl. pre-ban, LE-marked, and current unmarked. G21: use only in pre-ban, older LE-marked mags with 3955 follower & 10-rd mags. G22 through G35: pre-ban mags & older LE-marked mags (do not use with Tac-Lights).