... bits 2.Specification:17 1/2" 444.5mm 3.IADC:515 4.WOB:0.25--0.80KN/mm 5.sealing:rubber rings 1) ... .The HSN rubber O-ring provides adequate sealing for bearing durability.637Hard Formation TCI Tricone BitsThe 637 bits are used ... .The HSN rubber O-rin provides adequate sealing for bearing durability.IADC CODE:112 121 131,127 ,137,215 ... 635,637,712,737,837,832 (RD) supply 17 1/2" IADC 515 tci rock bits