These are Chrome Plated Matchless Nozzles for the Olsson Block or the Ultimaker 2+ series of 3D printers. The matchless nozzles are chrome plated to stay cleaner longer and has special internal channels inside the nozzle for optimum flow. They are made in Norway for the highest quality and tolerance by 3D Solex. Choose your nozzle size to match your preference for faster printing speed or more precise detail. Install by just screwing it into your Ultimaker 2+ or Olsson Block (sold separately).