Rocky Mountain Twist 953CO5/16SS Threaded Shank, Cobalt, 135° Split Point is for use on Steel (low and medium carbon), Steel Alloy, Stainless Steel, and Strength Alloys. Hard surface with high lubricity Industrial-Grade NAS Cobalt Steel (HSCO). 5/16" Fractional Size, 0.3125 , 1-1/4" Overall Length.