Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number U17643 found under Valve Restrictor Ch by Siemens Water Technologies Corp. The National Stock Number assigned to this part is 4820001280473, 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 U17643.