... N for hard stratum Description: It is a kind of washover tool, which is used to chear up the downhole rocks ... into:1. Type A,E,K,L for the junks washover.2. Type C,F,H,G for mending the top ... ,I,J,F,G,M,N for hard stratum washover or stabilizers washover. Main Models:TypeO.D.(mm)I.D.(mm)Length ... (mm)Min.hole(mm)Max.washover(mm)TXZ117117.6599.57500-1000120.6588.90TXZ136136.05108.61146.05101 ...