Useful aid when cooking using the sous-vide method as they prevent heat loss and evaporation of water. These balls serve as a replacement for a lid and can be utilized with any type of pot or container as they cover the surface of the water bath. I recommend using PET-G and only for cooking below 80°C. The ball features a flat bottom for better bed adhesion. Store-bought sous-vide balls are quite expensive, and I'd appreciate your comments and suggestions for trying out various materials.