Glass Petri Dish for Culturing Bacteria, Yeast, and Other Culture Cells Made of borosilicate glass, safe for autoclave sterilization, and reusable. Dimensions indicate the outer diameter of the bottom dish. Cover has a loose fit, with an outer diameter 6-7 mm larger than the bottom dish. This is by design to allow air or CO2 to easily diffuse; it is not a defect. Glass thickness is approximately 2 mm. Overall height ranges from 20 to 30 mm, higher for larger plates.