... Tricone Bits1)The 415 tci bits are used to drill low compressive strength, very soft formations.2 ... rate and added cutting structure durability in medium-to-medium hard formations.3)The HSN rubber O- ... Type Available Size: 6",6 1/2",7 1/2",8 1/2",9 1/2",9 5/8",9 7 ... the probability of cone-dropping to minimum.Main Type AvailableSize: 8 1/2",9 1/2",9 5/8",9 ... ",4 3/4",6",6 1/2",7 1/2",8 1/2",9 1/2",9 5/8",9 ...