Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 337.978 found under Seal Ring Metal by Webasto Thermosystems Inc. The National Stock Number assigned to this part is 5330011587159, 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 337.978.