Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number MC56 found under Spring Helical Tors by Insinger Machine Company The. The National Stock Number assigned to this part is 5360003165410, and the Federal Supply Class is 5360 Coil Flat Leaf And Wire Springs. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like MC56.