Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 129SP20 found under Gear Herring Bone A by Mack Trucks Inc. The National Stock Number assigned to this part is 2520003532759, 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 129SP20.