Spd Slot Hlsw 1-3/8dbox 1-3/8" Diameter, Bi-metal Hole Saw Tooth shape evenly distributes cutting force over a wider area of the tooth Patented tooth set and height works independently, with super efficiency Virtually indestructible, they will cut faster and cleaner and last longer than other hole saws Use Lenox arbor 2L, 3L, or 6L