Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 5421R1 4 found under Valve Regulating Fl by Schrader Bridgeport International. The National Stock Number assigned to this part is 4820011037121, and the Federal Supply Class is 4820 Valves Nonpowered. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like 5421R1 4.