... hole drilling air reverse circulation drilling. High Pressure RC Drilling bit Bit for down-the-hole drilling, air reverse circulation drilling ... drilling, geothermal well drilling, reverse circulation drilling.Bit Front designs:Complete compatible to be used with DHD hammerDHD330, DHD340, DHD350, DHD360, ... Convex Front, Flat Front, Concave Front, Concave DGR Front etc.Bit Dia. RC Drill Hammer and Bit