Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number X39-553 found under Cup Tapered Roller Bearing by Acf Industries Inc. The National Stock Number assigned to this part is 3110001424390, and the Federal Supply Class is 3110 Bearings Antifriction Unmounted. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like X39-553.