Specification: Shank Diameter: 1/4 inch Blade Diameter: 5/8 & 7/16 inch Suitable For: 1/4 & 3/8 inch bolts Material: Alloy steelNote: The router bit is NOT big enough to make a deep cut into the wood. You can cut a cut before using the keyhole bit to provides relief. Go easy on the feed and back off every couple of inches before resuming with the cutage Included: 2 x Keyhole Router BitWarm Tips: 1. The router cutters are very important to use the normal casing size, the tool must be fully inserted into the casing and tighten firmly, so that we can use in the process of cutting tool must provide clamping force, not only partially inserted into the casing, otherwise it will lead to fracture caused damage to the tool shank. 2. Please always notice to add some coolant (like water) when operating, in case the material temperature will get very high even get smoke because of the long time operating.