‧Shank Diameter：6.35mm ‧Shaft Diameter：3.5mm ‧Works with KAKURI Wooden Dowel-Xsmall It is useful by power drill tool. But don't use impact function by power impact drill. This drill is for Wood only. Don't drill deep over spiral part. Don't bring your face and hand close to turning drill. Don't touch drill blade, specially it is too hot just after use. Wear safety goggles in working. Keep out of reach of children.