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.
Specifications:

Type	Magazine Sleeve
Model	XD(M) 9/40 3.8" Barrel
Dimensions
Size	3
Material	Metal/Hardened Plastic
Action
Trigger
Safety
Thread Pattern
Finish	Black
Bolt Type
Hand
Hammer Type
Max Capacity