Springfield Armory X-Tension Magazine Sleeve XD(M) 45ACP Compact

A: It'll fit over the magazine. If your using your standard capacity magazines it would keep the magazine from locking in and it would be unable to feed, if you are using Promag 25rd high capacity magazines it would not fill in much of the Gap, so I'm not sure why you would want to use this with your 5" xdm, it wouldn't add anything to your gun, this doesn't increase the magazine capacity l, it only fills the gap left when running a full size magazine in a compact XDM.

A: If your xdm is a compact it will fit allowing you to extend the grip area whe you are using the mags for the full size gun. With a 5 inch barrel you most likely have a full size gun and this would not be needed

A: John, no Sir. The 5 inch XDM .45ACP is a full size Pistol. This sleeve is to allow full sized magazines, which you already use, to be used in smaller XDM .45ACP Pistols. Cheers and stay safe!