Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number F44-20-63-63 found under Seat Valve by Worcester Controls Corp. The National Stock Number assigned to this part is 4820004101940, 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 F44-20-63-63.