Recommended for very hard and fractured formations. Manufactured with high quality natural diamonds. Features 1.The interior is smooth2. ... Withstand difficult drilling conditions 3.With quality raw materials to suit the customer's requirements4. The ... shoes are used in various overbruden formations.Size Available:Q Series: BQ, NQ, HQ, PQW Series: RW, EW, AW, BW, NW, HW, PW ...