Drill Bits Walter Drillco® Nitro Heavy Duty Mechanic's Length Drill Bit Set, 29 Pieces, High Speed Steel, 350NW29 Bandfile The keys withstand more torque The keys withstand more torque and extend the life of the tool in the toughest jobsite conditions The 90 tooth ratchet delivers greater fastener access and an increase in strength during heavy duty applications thanks to its durable construction The Nitro Heavy Duty 135° Split Point Drill with a Nitride surface treatment that gives a hard protective layer to the drill (increases hardness without increasing brittleness) which is measurably harder than high speed steel Manufactured from a premium grade of M 7N molybdenum high speed steel