Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 3688-4 found under Screw Cap Hexagon H by Allison Transmission Holdings Inc. The National Stock Number assigned to this part is 5305005895484, 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 3688-4.