One 50mm (2") diamond coated hole saw / drill bits. The size is 50mm outside diameter and 10mm shank, can drill up to 35mm depth. These are the very same diamond core drill bits Tanya uses when demonstrating how to drill holes in fused glass donuts. 50mm can be used as your outside hole. AAE Glass carries several different sizes. These are quality diamond bits and we have used these same bits for years. A free video is available in the Education-Video section of our website. These drill bits are to be used in conjunction with a drill press, rotary tool or hand drill. Suitable for the use in drill hole on glass, marble, tile or granite. Please add water when drilling. 1" = to 25.4mm.