Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number C20SS1-4IN found under Valve Check by Deltrol Corp. The National Stock Number assigned to this part is 4820004555565, 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 C20SS1-4IN.