down the hole drilling Bit for down-the-hole drilling, air reverse circulation drilling. down the hole High Pressure RC Drilling bit Bit for down-the-hole drilling, air reverse ... .Bit Front designs:Complete compatible to be used with DHD hammer DHD330, DHD340, DHD350, DHD360, DHD380, SD18, N180 etcConvex ... 254mm, 279mm, 305mm, 330mm, 356mm, 381mm, 445mm, 555mm, etc. Down The Hole Drilling Bit