Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number A18 921 found under Gear Helical by Barber Greene Co. The National Stock Number assigned to this part is 3020008366410, 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 A18 921.