Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number C-5516W found under Washer Piston Seal Valve by Hydro Line Mfg Co. The National Stock Number assigned to this part is 4820011846593, 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 C-5516W.