... four to twelve, the size is 8-1/2”, 9-1/2”, 12-1/4”, 6”, 17-1/2”,4, the Rotary speed is form 10 ~300 ... used the featured about TCI&steel tooth tricone drill bits:1. High-strength, high flexibility, high temperature and high wear ... types: Size: Common sizes, 6.6-1/2, 7-7/8, 9-7/8, 10-5/8, 12-1/4 Various sizes also can be ... do not hesitate to contact me.mob:86-15631707417 12 1/4'' oil drill bit