Carbide-tipped cup blade. Bites significantly better than a normal Bi-metal blade. Also more durable. Perfectly suitable for e.g. for electricians, carpenters, kitchen fitters and everyone who works in the HVAC and plumbing field. Hole saws are well suited for wood, MDF board, plasterboard, plywood, plastic, building bricks, etc. Not intended for metal. Friction-reducing coating. The material to be sawn does not blacken, because heat is not generated from sawing to the same extent as from a regular hole saw.