Flat, clear petri dishes are manufactured from soda lime silica glass and will withstand repeated sterilization (wet or dry). Edges are beaded to provide greater mechanical strength. The bead also provides a means to equally space the side walls of the bottom and cover, reducing capillary action of any condensed moisture within. Dish bottoms feature a triangular enamel reference point for serial dilutions. Cover does not provide airtight seal. Chemical- and thermal-resistant.