1.best quality for 6"~17 1/2" 2.high quality,best price 4.number of blade :4,5,6,7,8,9,... 1,Application:1,Suit for drilling medium to medium-hard formations.2,Evolute asymmetrical blade cutter design and balanced bit load so that bit whirl is prevented .3,Composite gage protection and low torque design improve rate of penetration .4,CFD hydraulic balance design results in better bit cleaning and ...