Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number UP-21 found under Drain Cock Pump by Insinger Machine Company The. The National Stock Number assigned to this part is 4820011783308, 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 UP-21.