XDm 45 3.8 mag extension question

I have an XD .40 subcompact and ran into the same problem. Pierce makes a pinky extension that replaces the floorplate on your "subcompact" magazine. I love mine best $10.00 that I spent. It also doesn't change the rear grip profile for conclealing purposes. Here is a link to the product for your particular pistol. (Unless this is the product you are refering to, if so please disregard)

http://www.pearcegrip.com/Products/Springfield%20Armory/PG-XD45

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