Springfield XDm Magazine 11-Coil Spring and Follower Kit by Grams Engineering 

FKXM-11 (Follower Kit - for Springfield XDm 9mm & .40 mags, that measure up to 145mm long, (includes Grams Format Follower (XM) & 11 coil spring))

Grams Slide Lock Function

This "Follower Kit" is pre-tuned and requires no modifications for proper feeding function in a magazine tube of correct tolerances. The follower is designed for slide-lock function, but due to tolerance stacking of all of the slide lock system parts, modification of these parts may be necessary for proper function. Tuning of the mag tube may be required if the desired reliability or round count is not obtained.