... qualified. 2, Meta sealing. 3, Bit size: 8-1/2" ~ 12-1/4. 4, Connection: 4-1/2", 6-5/8" ... back of leg and seal.4. Bit's bear is enhancedtreatment, and prolonging te bit working life, reducing the ... marl, clay, unconsolidated sandstorm, salt, etc. Recommended Bit type: GHJ437, Drilling weight: 0.35~0.90 ... shale, clay, sadstne, soft limestone, etc. Recommended Bit type: GHJ517, Drilling weight:0.35~1.05 ...