made of chrome vanadium steel for adapting various square drives with, e.g., ratchets, sockets, etc. adaptor internal square 6.3 mm (1/4") on external square 10 mm (3/8") adaptor internal square 10 mm (3/8") on external square 6.3 mm (1/4") adaptor internal square 10 mm (3/8") on external square 12.5 mm (1/2") adaptor internal square 12.5 mm (1/2") on external square 10 mm (3/8") surface finish: satin chrome plated, Weight: 0.2866009406 Pounds, Manufacturer: BGS Do it yourself