drill bits,drill segments,hss drill bits are used for cutting all kinds of stone.diamond drills.over 20years experience in China ISO9001:2000,SGS certification. Electroplated diamond core drill bit for mine, coal mine drill bits. all kinds of drill bit. the size is following:1, Double tube drill:Φ28,Φ36,Φ46,Φ59,Φ60,Φ66,Φ75,Φ76,Φ91,Φ94,Φ1102,single tube drill:Φ36,Φ46,Φ59,Φ75,Φ91,Φ94,Φ110,Φ130,Φ170 ...