[Wikipedia excerpt: ‘…… Petri dishes are usually cylindrical, mostly with diameters ranging from 30 to 200 mm, and a height to diameter ratio ranging from 1:10 to 1:4. Squarish versions are also available. Petri dishes were traditionally meant to be reusable and made of glass; often of heat-resistant borosilicate glass for proper sterilization at 120–160 °C. Since the 2010s, plastic dishes, usually disposable, are also common. Petri dishes are often covered with a shallow transparent lid, resembling a slightly wider version of the dish itself. The lids of glass dishes are usually loose-fitting. Plastic dishes may have close-fitting covers that retard drying of the contents. Alternatively, some glass or plastic versions may have small holes around the rim, or ribs on the underside of the cover, to allow for ventilation of the air space over the culture and avoid water condensation that may be a problem that needs some attention. Some Petri dishes, especially plastic ones, usually feature rings and/or slots on their lids and bases so that they are less prone to sliding off one another when stacked. Small Petri dishes may have a protruding base that can be secured on a microscope stage for direct examination…..’ ].