Bi-Metal Speed Slot Hole Saw With T3 Technology, 5-1/2, Lenox Tools Model Number The LENOX Tools Bi-Metal Speed Slot Hole Saw with T3, 5-1/2"-140mm, has enhanced tooth geometry that cuts 50% faster than previous LENOX hole saws. Twice as durable as our previous generation when cutting through metal, this bi-metal hole saw features thicker walls to minimize tooth loss and improve durability. A staircase SPEED SLOT has a wide slot placed low on the 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 the saw. 10% taller than previous models, it delivers cleaner cuts through two-by lumber. 2X more durable with 50% longer life than previous LENOX hole saws Increased wall thickness improves durability and minimizes tooth loss Optimized tooth design penetrates metal with ease Larger, sharper teeth for faster cutting SPEED SLOT staircase design for easy plug ejection