1-3/8" hd self-feed bit. Aggressive spur provides fast material penetration. Optimized cutting geometry provides longer bit life. Open tooth design allows for more resharpenings. 7/16" ball groove shank allows for quick change applications. Length: 1-3/8", Shank Diameter: 7/16" No. DW1634: Length: 1-1/2", Shank Diameter: 7/16" No. DW1635: Length: 1-3/4", Shank Diameter: 7/16" No. DW1636: Length: 2", Shank Diameter: 7/16" No. DW1637: Length: 2-1/8", Shank Diameter: 7/16" No. DW1639: Length: 2-9/16", Shank Diameter: 7/16"