This backstrap sleeve fits over a full size XD-M magazine in 9mm or 40 S&W to make your 3.8" XD-M Compact pistol frame fit a high capacity full size magazine. This black polymer piece does not extend the length of the magazine. Type Magazine Sleeve Model Backstrap Sleeve Finish Black Series X-Tension Sleeve for Backstrap Caliber 9mm Luger Material Polymer Brand Fit Springfield Armory Model Fit XD-M Compact