1.high quality diamond bit 2.suitable for all kinds of strata 3.high cost effective JSA-class diamond bit to ... meet the demand of the domestic market practice, the use made of quality ... work for the 5-6mm, product works excellent, high quality, suitable for all kinds of strata, a total ... ± 1, HRC43 ± 1, HRC45 ± 1 JSA level - high quality diamond bit (blue)