Toni System's frame mount for Springfield fits the XDM in both 4.5 and 5.25 inch versions, and the HS Produkt SF19 built on the same frame.
What it does
The machined aluminium weight bolts under the dust cover, ahead of the trigger guard. Putting mass there resists the upward flip of the muzzle, so the sights stay closer to the target during fast strings.
Balance
A polymer pistol is light at the front. Adding weight ahead of the grip shifts the balance forward and helps the gun settle between shots.
Accessory points
Built-in attachment points let you add a thumb rest, or a short rail to hang a light, with the hardware already provided.