The GLOCK 10 Coil Magazine Spring for 9MM / 10MM / .357 / .40 / .45 Auto models (33510) can work in 17 round magazines, 15 round magazines, and pre-ban magazines.
Models: G17, G17L, G18, G20, G21, G22, G23, G24, G25, G26, G27, 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)