Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number B50-20 found under by Pro Dexinc. The National Stock Number assigned to this part is 3010011510842, and the Federal Supply Class is 3010 Torque Converters And Speed Changers. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like B50-20.