Titan Tools 17408 Adapter and U-Joint Set - 7 Piece Chrome vanadium steel Adaptor sizes: 1/4 inch (f) to 3/8 inch (m), 3/8 inch (f) to 1/4 inch (m), 3/8 inch (f) to 1/2 inch (m), 1/2 inch (f) to 3/8 inch (m) U-joint sizes: 1/4, 3/8, and 1/2 inch