Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 637-00004 found under Seal Plain Encased by Parker Hannifin Ltd. The National Stock Number assigned to this part is 5330013324061, 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 637-00004.