Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number B21-00563 found under Gear Internal by Curtis Straus Llc. The National Stock Number assigned to this part is 3020001418874, and the Federal Supply Class is 3020 Gear Pulley Sprocket And Transmission Chain. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like B21-00563.