Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 12.1257.00 found under Valve Assembly by A Dec Inc. The National Stock Number assigned to this part is 4820016702428, 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 12.1257.00.