Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number F4T4BL found under Lamp Fluorescent by Lamp Industry. The National Stock Number assigned to this part is 6240005004146, and the Federal Supply Class is 6240 Electric Lamps. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like F4T4BL.