DTH hammer,DTH hammer bit,Down the hole bit,rock drill,rock drilling,overburden bits,Hammer,Drill bit,Hihg air pressure 4High air pressure DTH BitsDTH Bits seriesDrill BitBit Dia.(mm)NO ... and manufacture according to customer's requirement of the Bit DiaNo.air holescarbide button shape and the face shape. 4 Inch DTH hammer bits