Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 5040-0257 found under Holder Lampholder by Keysight Technologies Inc. The National Stock Number assigned to this part is 6250002310778, and the Federal Supply Class is 6250 Ballasts Lampholders And Starters. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like 5040-0257.