A small hole type hole saw that allows you to drill the box in one time. No need to adjust sharpening! Ready to install wiring fixtures.(Opening hole diameter: H 4.0 inches (102 mm) x W 2.1 - 2.2 inches (54 - 56 mm)); Can be drilled by posts or walls (up to 13.6 mm) is OK; Just attach it to your charging screwdriver. (14.4 V recommended) Comes with a level to allow straight drilling; For use with reinforced pretend boards, and for use with toilet boards; Hole saw opening diameter L 4.0 inches (102 mm), W 2.1 - 2.2 inches (54 - 56 mm); Cutting depth strengthening board : 0.5 inches (12.5 mm) x 2 mm), Hex shank diameter 0.35 inches (6.35 inches (6.35 mm). Electric screwdriver (recommended) 14.4 V rechargeable drill driver *Can also be used with 12 V and 18 V. Please use the drill mode of the charging driver with the left rotation (L). Set Contents: Oval hole hole saw, replacement blade S (Part number: FHBH3S) (reinforced pretend board x 1), EG attter 2, drill gauge for 2, hex key (for side drills), hard case. *Cannot be used with panel box for small hole holes.(including iron) *Not compatible with aftermarket boxes.