Ritter M-11 Ultraclave Automatic Sterilizer The M11 is a larger addition to the Ritter line of automatic autoclaves with reliability and efficiency as one of its many assets. The M11, like the M9, features a door that opens automatically and quietly, making sterilization a set-it-and-forget-it procedure. Its unique 11" by 18" chamber gives it the distinction of the largest sterilizing capacity of any standard countertop autoclave on the market, making it perfect for larger packs and instruments.