3/8" Diamond Core Drill Bit For Granite Concrete and Marble | Free Beginner's Drilling Guide | Free Shipping | 100 % Money Back Guarantee 3/8" Diamond Core Bit for Granite, Marble and Concrete Fits your drill or drill press, no special tools Free 4 page drilling guide 100% money back guarantee, Free shipping in the US Sintered, not electroplated, to last longer