Lenox Tools Bi-Metal Speed Slot Hole Saws with T3, 1-3/8"-35mm, have enhanced tooth geometry to cut 50% faster than previous Lenox hole saws. Twice as durable as our previous generation when cutting through metal, these bi-metal hole saws feature thicker walls to minimize tooth loss and improve durability. Staircase SPEED SLOTS have wide slots placed low on each hole saw and multiple leverage points to make it easy to work plugs out with a screwdriver. This design effectively removes sawdust and chips and helps prevent plugs from becoming stuck in each saw. 10% taller than previous models, they deliver cleaner cuts through two-by lumber.