96-well microplates are available in flat (F), conical (V), and round (U) bottom varieties. Polypropylene microplates offer higher temperature resistance and are less reactive than polystyrene. Each well in the microplate is designed to have a raised rim to reduce cross contamination, and to provide a better fit to the corresponding raised ring in the lid. Lid use reduces excessive evaporative fluid loss. Sterile plates are gamma irradiated.