Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 20503 found under Bit Wire Wrapping Tool by Ostby Barton Test Probes Division. The National Stock Number assigned to this part is 5130000185851, and the Federal Supply Class is 5130 Hand Tools Power Driven. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like 20503.