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