Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number MS17990-421 found under Pin Quick Release by Alcoa Fastening Systems Ltd. The National Stock Number assigned to this part is 5315002003708, and the Federal Supply Class is 5315 Nails Machine Keys And Pins. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like MS17990-421.