Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 4320 found under Screw Shoulder by Drs C3 And Aviation Company. The National Stock Number assigned to this part is 5305009957091, 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 4320.