Big Horn 19123 7pc Split Ring - Stop Collar Set. Designed to grip the entire diameter of your drill bit. Used to accurately control the depth of the hole you are drilling. These split collars will hold where you put them every time. Sizes include 1/8", 3/16", 1/4", 5/16", 3/8", 7/16", and 1/2" 7-piece set comes with allen wrench.