Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 4253-137W found under Valve Check by Consolidated Welding And. The National Stock Number assigned to this part is 4820007321089, 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 4253-137W.