Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number R50055 found under Valve Check by Kerotest Manufacturing Corp. The National Stock Number assigned to this part is 4820002872301, 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 R50055.