For contact techniques. “Rodac” is an acronym for Replicate Organism Detection and Counting. Well in center will hold 16 ml of agar, which when cooled, leaves a bed raised approx. 1 mm higher than rim of dish. The area of agar bed is approx. 25 sq. cm with Quebec-style grids of one centimeter squares. Agar is protected by a cake-box type lid. Made of polystyrene.