XDM 9/40 OPEN magwells are CNC machined from aluminum or brass and the colored aluminum magwells are anodized for durability. This magwell was specifically designed for USPSA OPEN and LIMITED divisions. The OPEN magwell has a HUGE opening but is also ergonomically designed not to interfere with your grip. The unique attachment method requires that you grind the backstrap even with the top of the magwell opening or purchase a prefit #2 backstrap. This is for full sized XDM 9mm and .40 frames only. For use with the #3 backstrap if you grind the back of the insert to fit the profile of the magwell. Not recommended for use with #1 backstrap. Does NOT fit with factory base pads, modification required to fit. Weighs 1.8 oz.