This C.K Hex Allen Key Set is constructed from high quality chrome vanadium steel that has been hardened and tempered to ensure long-lasting strength and durability. The clip holder is manufactured from heavy-duty, nickel plated steel. The C.K Imperial Hex Allen Key Set is a handy addition to all toolboxes, and consists of the following sizes: 3/32", 1/8", 5/32", 3/16", 3/8" and 5/16".