Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number FT4A00S503 found under Fuse Cartridge by Wayne Kerr Electronics Inc. The National Stock Number assigned to this part is 5920012859879, and the Federal Supply Class is 5920 Fuses Arresters Absorbers And Protector. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like FT4A00S503.