Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number MS21916J4-3 found under Reducer Boss by Society Of Automotive Engineers Inc. The National Stock Number assigned to this part is 4730008518466, and the Federal Supply Class is 4730 Hose Pipe Tube Lubrication And Railing Fittings. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like MS21916J4-3.