Bon Chef Cold Wave Bowl, 9 7/8 inch Diameter -- 1 each.Bon Chef proudly introduces its patented 3 Wall Cold Wave Miracle Bowls. Pre-freezing these bowls will keep your food cold for 8 hours at ambient temperature. Outer air chamber prevents the bowl from sweating while keeping the inner chamber gel frozen. Each bowl comes with a stackable plastic lid. In out test results, a bowl was put in the freezer until gel was frozen. 35 degree F potato salad was placed in the bowl without lid and stirred every 30 minutes. After 8 hours the potato salad was at 38 degree F.