These solid brass inserts fit into your router base plate to reduce the gap around the router bit. Not only is this safer, but it also reduces tear-out and helps support smaller work pieces. Supplied in a set with openings of 1/4”, 3/8”, 1/2”, 5/8”, 3/4”, 7/8”, and 1”, plus a retaining nut. Openings are slightly oversize for tool clearance. Fits any router with a standard 1-3/16” diameter recessed hole for template guides.