4 piece, natural stone, tile bit set, consists of: 1/8", 3/16", 1/4", 5/16" bits, multi-grind head, designed with multiple cutting edges for harder tile materials, fast drilling in hard materials, specialized carbide tip, centers for no-skate drilling & greater ease of use, high quality carbide material, provides longer life in hard materials, 3 flat shank offers outstanding bit grip to avoid slippage, engineered for use in natural stone tile, slate, granite & other specialty tile materials specialty tiles that may be harder than normal tile, not recommended for use on porcelain tiles, compatible with hammer drills.