Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 6421 found under Valve Control by Rosco Mfg Co. The National Stock Number assigned to this part is 4820011057487, 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 6421.