Product Description The IRWIN� 20mm Bi-Metal Hole Saw cuts through a variety of materials, including: Aluminium, Copper, Iron, Stainless Steel, Wood and Zinc. The electron beam welded High Speed Steel (HSS) cutting edge ensures stronger, longer lasting teeth. Precision set teeth provide faster penetration and cutting. And, the bi-metal construction delivers toughness and long life. WELDTEC� Technology delivers enhanced durability and higher cutting speed. Tooth design provides up to 100% longer life and 50% faster cutting vs previous IRWIN models 4,5/5,5 Variable TPI for faster cuts, less torque build-up and enhanced chip removal. Variable gullet depths for more efficient chip clearance Bi-Metal construction and thick backing plate for increased life and durability, capable of tackling the toughest of jobs.