Surface set diamond core bits ensures sufficient overlap to prevent premature wear of the matrix. Surface-Set Diamond Bits are set with a ... rotational speeds and bit loads are insufficient to use impregnated diamond bits due to drilling equipment limitations. Series Size AvailableQ series ... ,BWT,NWT,HWT(Single Tube/Double Tube)WG SeriesEWG,AWG,BWG,NWG,HWG(Single Tube/Double Tube)WM SeriesEWM,AWM,BWM, ...