If you have watched the documentary "Jiro's Dream of Sushi," you may have noticed that the cutting boards used are not wood but synthetic boards. Likely from the professional line of Asahi. Many sushi restaurants and professional chefs rely on these boards. So, what is special about these yellowish-colored pieces of synthetic rubber? They are made of high-density antibacterial material that is easy to clean and stays hygienic. Unlike wooden boards, which will dish easily over time, these boards will remain flat for a long time. Some restaurants have been using the same Asahi boards for over 40 years. While they are dense, they are still made of rubber, which actually holds the edge of your knife longer than pure wood. Wood particles are incorporated into the material to provide a nice feel and sound when cutting. They also allow sanding down the board once it is really worn out.