EZ Bioresearch Sterile 100 mm X 15 mm Petri Dish with Lid, vented, 2 x Pack of 10 Optically clear Petri Dishes made from virgin polystyrene plastic. 20 dishes (2 x pack of 10 dishes). Sterile made for laboratory use. Venting rib cover for optimum bacterial culture growth. Note: 100 mm is a NOMINAL value. The actual size is in the range of 92-93 mm. It is the norm in the biotech industry.