Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 3421 SFW 8521 found under Axle Assembly Automotive Driving by Rockwell International Corp. The National Stock Number assigned to this part is 2520015179512, and the Federal Supply Class is 2520 Vehicular Power Transmission Components. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like 3421 SFW 8521.