Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number ES138C2 689A923 AT found under Washer Flat by Lucent Technologies Inc. The National Stock Number assigned to this part is 5310012930408, and the Federal Supply Class is 5310 Nuts And Washers. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like ES138C2 689A923 AT.