... bits manufacturer 2>First-class quality with most competitive price 3>API Model115,117,121,227,417,437,517, ... bearing(HJ), rubber bearing(HA)Advantagehigh quality with reasonable price because of used productFormationsoft and medium formation, hard formationButton bitsmall tooth ... used drill bits:1>the abrasion of the button bits2>the quality of the bearingshipment of steel tooth bits : API steel ...