This is a modular mounting system for Milwaukee tools. I have provisions to mount each rack to the neighboring one using #10 hardware, and the racks can be mounted to either the underside of a shelf, or to rails with t-nuts on a 6 inch spacing (5/16 hardware). This model is for Milwaukee 2853, which is the gen 3 or 3.5 impact driver. Im sure it fits almost any impact driver out there, but was designed specifically for these models