Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 20539C found under Valve Regulating Fluid Pressure by O C Keckley Company. The National Stock Number assigned to this part is 4820002886971, 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 20539C.