Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 3974-5-CSPC3 found under Poppet Valve Assembly by Harris Environmental Systems Inc. The National Stock Number assigned to this part is 4820012557680, 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 3974-5-CSPC3.