Flat, clear PYREX VISTA dishes will withstand repeated sterilization (wet or dry). The edges are beaded to provide greater mechanical strength. The bead also provides a means to equally space the sidewalls of the bottom and cover, thereby reducing the capillary action of the condensed moisture on the sides. They are not affected chemically or thermally by any of the methods commonly employed in laboratories where sterilization is routinely used. The covered dish is not airtight. Bottoms also have a triangular enamel reference point for serial dilutions.