Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 556-31880 PC.17 found under Gasket by Permutit Co The. The National Stock Number assigned to this part is 5330012469824, and the Federal Supply Class is 5330 Packing And Gasket Materials. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like 556-31880 PC.17.