Keyhole cutter set with 6.35 mm shank, with 5/16", 3/8", 1/2" cutter diameter. C3 micro-grain carbide blades, body made of high-quality alloy steel. Build-up heat-resistant Teflon coating. Suitable for solid wood, particle board, MDF, plywood, etc. Produces very nice, clean cuts with minimal re-sharpening. These T-slot cutters for hex head screws. Designed for handheld and table-mounted routers, cannot be used in electric drills.