Speed: aggressive feed screw design allows the bit to pull through the wood faster and without effort, resulting in faster drilling. Replaceable SWITCHBLADE™: The SWITCHBLADE™ replaceable blade system ensures your blade is always razor sharp. It increases productivity by eliminating resharpening downtime and it increases the overall life of the bit. Application: suitable for all general contractors, electricians, plumbers and HVAC engineers who require to drill through holes in wood for all types of pipe, vents and wire trunking. Each Selfeed bit is supplied with 2x blades, 2x replaceable feed screws, 2x set screws and 1x allen key.