IADC CODE 2-1-1
Non-sealed ball and roller bearing
FORMATION
Medium strength with hard streaks (firm shales, histones, broken formations, dolomite, anhydrites).
CUTTING STRUCTURE
The TO21 has the same tooth length, moderately spaced on intermeshing row, spaced closer than TO13, its incorporates medium cone offset for balanced gouging/scraping and crushing/chipping actions.