This magazine is intended for use in compact sized XD-M Elite 10mm models, effectively converting the grip from compact to full size. The included magazine sleeve, as noted, aligns with the installed backstrap already on the pistol creating a seamless transition from compact to full size and allowing the user extra capacity in a compact platform. To ensure proper fitment, magazine with sleeve #1 needs to be used with backstrap #1. Requires removal of magwell for proper fitment on XD-M Elite Compact models. Current production 10mm XD-M Elite pistols ship from factory with Backstrap #1 installed. XD-MA(R) Compact 15-Round Extended Magazine, with magazine sleeve 1, for use with backstrap size #1 - 10mm