Radiation sterilized; sterile if sleeve is unopened Top and bottom edges are squared off (not rounded) to provide a firm, sure grip Bottom is flat so medium spreads evenly over the entire dish bottom Three ventilation ribs allow free air circulation and reduce condensation during incubation Lid skirt is flared just enough so that it can be replaced quickly after streaking Place lid upside down on dish to close off dish from outside environment Raised-Ridge Petri Dishes Stack high and remain stacked Minimum of slipping, sliding, and resulting scratches Beveled-Ridge Petri Dishes Ideal for automated filling systems Remove dishes easily from the center of a stack No-Ridge Petri Dishes Ideal for use in automated systems