1/2 1/4 73mm: 1/4in hex shank to 12.7mm square head. 3/8 1/4 65mm: 1/4in hex shank to 9.53mm square head. 1/4 1/4 65mm: 1/4in hex shank to 6.35mm square head. 1/2 1/4 50mm: 1/4in hex shank to 12.7mm square head.
eBay