XDM 9/40 extended base pads are CNC machined from aluminum and hard anodized. This lengthens the magazine .25 to make for easier, more reliable magazine changes. They also allow you to use a magwell without adding capacity to the magazines. They are perfect for the large magwells.
If your magazines factory base pad has a ROUND hole in the center, these base pads will work for you.
If your magazines factory base pad has an OVAL hole at the front, you will need the SQUARE base pads.