Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 5421999-31 found under Hose Preformed by W W Grainger Inc. The National Stock Number assigned to this part is 4720015864662, and the Federal Supply Class is 4720 Hose And Flexible Tubing. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like 5421999-31.