knurling / drilling bit with SK blades and guide drill SDS+ attachment high-quality SK blades (SK - sintered carbide), long service life, fast penetration of material the guiding - centering drill makes work easier and precisely guides and holds the crown in the desired place < span style="color: black"> for drilling larger diameters in concrete, aerated concrete, bricks and similar masonry materials the crown is not suitable for drilling reinforced concrete