This is a BLAIR BLR11108-3 3/8" Rotabroach Spot Well Cutter. 11,000 Series Rotobroach cutters 3/8" (3 pk) This series cut holes 3 times faster & last 10 times longer than twist drills or hole saws, for precision hole making in sheet metal & frame materials uo to 1/2" thick. Blair Rotabroach annular cutters made clean, burr-free round holes with no deforming of stock or damage to the surrounding material. There's no dead sone, so less thrust is required & no deforming of stock or jagged edges occurs. Multiple cutting teeth, precision ground which allows for a long tool life.