Inert 20mm Netherland armor-piercing target practice round used in the Rheinmetall Mk 20 Rh-202. This 20x139mm casing is made of steel and is in good condition. The Rheinmetall Mk20 Rh-202 is a 20mm autocannon designed and produced by Rheinmetall. It fires the 20x139mm ammunition originally developed for the Hispano-Suiza HS.820.