These are perfect for reshaping and restoring edges on many cutting and drilling tools. Their light weight and small size make them handy for jobs where bigger stones are hard to handle or just won't fit. Diamond-coated surface is 3/4" x 2" on a 6" plastic paddle. Medium is 270 grit. This grit is not recommended for resharpening carbide-tipped router bits; relatively large abrasive grains can shatter brittle carbide edges and leave them worse than when you started. If a bit needs more than touch-up honing, we recommend that you send it out for professional regrinding, then improve and maintain it with fine and extra-fine diamond paddles.