... bits, cross bits, buttons bits, DTH bits with high, medium and low air pressure, symmetric drilling tools, eccentric drilling tools, standardized API system casings, bit ... and reliability of the products.Tapered Drill BitType --Chisel Bits / Cross Bits / Button Bits Diameter---28mm,30mm 32mm,34mm,36mm, ... R28,R32,R38,T38,T45,T51. Integral Drill Rod---H19/H22, Diameter---20mm - 42mm. tapered drill bit