5'' dth drilll hammer high pressure down the hole hammer wind pressure:0.5-2.5mpa Impact frequency :25 match bit :138-152 With yeas of experience, now Zhongrui can manufacturer the best quality DTH drill bit, DTH hammer and chisel bit, thread button bit. 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" ...