3"-8" dth hammer DHD, COP model 4"-8" quick hammer High drilling ... of experience, now Zhongrui can manufacturer the best qualith DTH drill bit, DTH hammer. Now we can supply 90mm-254mm(3.5 ... "-10") DTH hammer, 340,350,360,380, COP44, COP54, COP64, COP84 , 3"- ... 8" DTH hammer, 340,350,360,380 4",5",6",8" quick ...