... air consumption 2. Straightness and hole quality 3. High penetration rate DTH drill hammer With yeas of experience, now Zhongrui can manufacturer the ... 90mm-254mm(3.5"-10") DTH drill bit, 340,350,360,380, COP44, COP54, COP64, COP84 , 3"-8" DTH hammer, 340,350,360,380 ... 4",5",6",8" quick hammer with very good price ...