Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number B21-00549 found under Gear Spur by Curtis Straus Llc. The National Stock Number assigned to this part is 3020002393842, 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 B21-00549.