Chuck key tightens the jaws of the 1/2 In. capacity chuck 48-66-1360, 48-66-1370, and 48-66-1381. Key holder 48-66-4040 should be used to attach this chuck key to the cord set. No. 48-66-3280: Chuck Size: 1/2 In., Pilot Size: 1/2 In., Handle Type: T-Handle, Pkg Qty: 1, Package Type: Card