Manufactured from chrome vanadium steel. Hardened and tempered for strength and durability. Ball ended for use at an angle of up to 25o where access is restricted. Set is supplied in a Clip holder for convenient storage and contains sizes 5/64, 3/32, 1/8, 5/32, 3/16, 7/32, 1/4, 5/16 & 3/8".