Durable hardened steel construction arbor with round shank. No. 49-56-6950: Shank Diameter: 1/4", Hole Size: Up to 1-3/16", For Use With: 1/4" and Larger Drill Chuck, Pkg Qty: 1, Package Type: Clamshell No. 49-56-7010: Shank Diameter: 3/8", Hole Size: Up to 1-3/16", For Use With: 3/8" and Larger Drill Chuck, Pkg Qty: 1, Package Type: Clamshell