1.best quality for 6"~17 1/2" 2.high quality,best price 4.number of blade :4,5,6,7,8,9,... Specifications1.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 ...