Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 303189 found under Back Up Ring Preformed Packing by Mastsystem Intl Oy. The National Stock Number assigned to this part is 5330016162372, 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 303189.