These disposable standard size Petri dishes are molded from medical grade virgin polystyrene and are radiation sterilized for general microbiological use. Feature optically clear top and bottom surfaces with consistent flatness for even distribution of media. Dishes are easy to grip and and have an anti-slip ring which offers stacking stability. Ventilation ribs reduce condensation during incubation and allow free air circulation. Packaged in sterile sleeves of 20 dishes.