... bit, button bit 2.Sizes range from 3 7/8" to 26" . 3.Reliable bearing and lubrication sys 1.Cutting ... and hardfacing on the shirttail increases gauge holding capability. 3. Bearing Structure Air cooling roller bearing package. Balls ... 537….……….. ………………………………12 1/2 211, 121, 241, 537….14 3/4 131, 211, 537, 517….15 1/2 211, ... 241, 537….………..………………………………26 131, 211, 537, 517…. tungsten carbide drill bits