Include impregnated, heavy-duty, surface-setcasing shoes ( the standard casing shoes and the rod casing shoes bits)The crown include flat face and "v" ring design, the impregnated casing shoes bits are good for sand, boulders, gravel and clay. The Surface-set casing shoes cut through boulders easily, and also are suitable for different overburden formations.Casing shoe bits: AW, BW, NW, HW, PW SW, Rod casing shoe: BQ, NQ, HQ, PQ