Hardened and tempered chrome-vanadium steel. Spring-loaded ball bearing. Fully polished and nickel chrome-plated for durable corrosion resistance. Supplied on storage rail. Contents: 1/4″F x 3/8″M, 3/8″F x 1/4″M, 3/8″F x 1/2″M, and 1/2″F x 3/8″M Hardened and tempered chrome-vanadium steel. Spring-loaded ball bearing. Fully polished and nickel chrome-plated for durable corrosion resistance. Supplied on storage rail. Contents: 1/4″F x 3/8″M, 3/8″F x 1/4″M, 3/8″F x 1/2″M, and 1/2″F x 3/8″M