The Starrett PT28314 Collet Adaptor is a time saving accessory for our 827 Series edge finders. It allows quick installation and removal of the edge finder, eliminating the need for collet changes on Bridgeports and similar machines. It can also be used with any other attachment with a 3/8-Inch post. The progressive steps are: 1/4-Inch, 5/16-Inch, 3/8-Inch, 1/2-Inch, 5/8-Inch, 3/4-Inch and 1-Inch. Step depths vary from 100-Inch to 200-InchTime saving accessory for 827 Series Edge FindersEliminates the need for collet changes on Bridgeports and similar machinesCan also be used with any other accessory with a 3/8-Inch postProgressive steps are: 1/4-Inch, 5/16-Inch, 3/8-Inch, 1/2-Inch, 5/8-Inch, 3/4-Inch and 1-InchStep depths vary from 100-Inch to 200-InchIt allows quick installation and removal of the edge finder, eliminating the need for collet changes on bridgeports and similar machinesIt can also be used with any other attachment with a 3/8" postStep depths vary from 0.100" to 0.200"The progressive steps are: 1/4", 5/16", 3/8", 1/2", 5/8", 3/4" and 1"This is a timesaving accessory for edge finders