JZ 3 1/2" IADC 137 Kingdream Cone cactus Certification:API&ISO Delivery iterm:Sea/Air Delivery port:Tianjin/China 517Medium Formation TCI Tricone BitsThis design provides a fast drilling rate and added cutting structure durability in medium-to-medium hard formations .The HSN rubber O-ring provides adequate sealing for bearing durability. More size Model114, 126, 117, 127, 437, 517, 537, 617, 637, ...