Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number U-539616 found under Valve Cartridge Flo by Triumph Thermal Systems Inc. The National Stock Number assigned to this part is 4820011933067, 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 U-539616.