Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number B312001099-1 found under Washer Recessed by Singer Co The. The National Stock Number assigned to this part is 5310002495178, 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 B312001099-1.