... newest rock drilling theory.2. Smooth performance and long service life of GM series DTH hammer due to high quality alloy steel ... main products are:1. Similar or equal DHD, COP and SD series hammers, our DTH hammers includeG24(2"),G3.5(3"),G44 ... "),G64(6"),G84(8")2. Similar or equal DHD, COP and SD series hammers,Our DTH bits range include85mm, 90mm, 95mm,100mm ...