These are two different orientations of T-Track stops. The can be used on standard T-Track. The hole is made for standard 1/4 hex bolts, but if you slightly enlarge it with a 5/16 drill bit then you can use it with 5/16 t-track bolts. Add a bolt and a corresponding star knob and you then have a set of stops that can be used anywhere you have T-Track installed. I use them on my workbench, miter saw station, and drill press.