Fits the 10mm Glock 20, 29, 40 Extended 30-round capacity Due to the wide variety of extensions for Glock, our mag base is designed to be compatible with Glock extensions ETS mags won't crack or break, are resistant to heat, cold, UV and harsh chemicals - won't become brittle over time. ETS mags come with enhanced features like non-tilt followers, creep-resistant feed lips and clear body allowing you to see count and ammo type - leaving nothing to chance. Advanced Polymer Benefits: Extreme Impact Resistance - won't crack or break when dropped Very resistant to harsh chemicals Superior heat, cold and UV resistance - won't become brittle over time even when exposed to harsh environments or extreme cold Translucent body - allowing you to see your ammo count and type Creep resistant - the feed lips and body won't spread when being stored long term even when fully loaded