Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 99-4053 found under Screw Cap Socket Head by Donallco Inc. The National Stock Number assigned to this part is 5305000500353, and the Federal Supply Class is 5305 Screws. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like 99-4053.