water well drilling hammer 350,350,360,380 wind pressure:0.5-2.5mpa Impact frequency :25 match bit :152- With yeas of experience, now Zhongrui can manufacturer the best qualith DTH drill bit, DTH water well drilling hammer . Now we can supply 90mm-254mm(3.5"-10") DTH bit, 340,350,360,380, COP44, COP54, COP64, COP84 , 3"-8" DTH water well drilling hammer, 340,350,360,380 4",5",6",8" quick water ...