Triangle shank diamond core drill bits diameter 8mm 5/16",diamond length 10mm,total length 65mm,triangle shank-fit. Vacuum dry/wet brazed diamond drilling bits Core bits with triangle shank. Wax are inserted to the drill bit for cooling and Lubrication, without adding water.designed with groove in the side of drill bit for removing stone chips. Triangle shank design can be gripped tightly that won't slip out easily,used in 10mm (3/8 in) Hand Drill, Bench Drill. Multi-purpose drilling for granite & marble,masonry,concrete,tile/ceramic,stone,etc.