This is a time-saving accessory for edge finders with a 3/8" shank. The collet adapter allows quick installation and removal of the edge finder, eliminating the need for collet changes on Bridgeports and any milling machines. It can be used with any attachment with a 3/8" shank. The progressive steps are 1/4", 5/16", 3/8", 1/2", 5/8", 3/4" and 1". Step depths vary from .100" to .200". Most times, the shank of the cutter you intend to use is not the same size as the edge finding tool. You would have to use one collet to hold the edge finder, align the work, and then switch collets for the mill work. The edge finder adapter eliminates swapping collets - which saves time and improves accuracy. Use with 25-010, edge finder or 25-015, Wiggler Center finder set, or 25-020, Laser Edge and Center finder. You may need to cut spacers for the fixture depending on the shank of your tooling.