Bit Size: 6.25" New 6 1/4" Walker- Mcdonald Mill tooth rock bits available in medium-soft, medium and medium hard formations. 3 1/2" api regular pin. Air or fluid applications. $695 Bit Size 6.25" CAPTCHA Get new captcha! What code is in the image? Enter the characters shown in the image. This question is for testing whether or not you are a human visitor and to prevent automated spam submissions.