Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number A18 20 found under Ring Backup by Ortman Fluid Power Quincy Compre. The National Stock Number assigned to this part is 5365007257276, and the Federal Supply Class is 5365 Bushings Rings Shims And Spacers. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like A18 20.