Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 4B1291 found under Screw Machine by Caterpillar Inc. The National Stock Number assigned to this part is 5305009592723, 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 4B1291.