Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 509639 found under Insulator Disk by Litton Systems Inc. The National Stock Number assigned to this part is 5970009552455, and the Federal Supply Class is 5970 Electrical Insulators And Insulating Materials. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like 509639.