... due to the special innerstructure of GM series DTH hammer designed according to newest rock drilling theory.2. ... performance and long service life of GM series DTH hammer due to high quality alloy steel materialsand advanced processing ... SD8QL40,QL50,QL60,QL80CIR65,CIR80,CIR90,CIR110COPROD89,COPROD102,COPROD127 Hammer typeBitsFace designAPI threadDiameterWork pressureG24(2")76/80mmFlat/Concave/ ...