This HDC 3pc. U-Joint Socket Adapter Set is made of drop-forged, hardened chrome vanadium steel construction for strength and durability. Also a nickel-chrome finish for corrosion resistance. The pivoting socket ends allow for greater maneuverability in cramped, close spaces which make them great for automotive uses and other applications. It includes the 3 major drive sizes 1/4'', 3/8'', and 1/2''.