Corning Polystyrene Universal Microplate Lid without Corner Notch, Sterile Lids are made of rigid polystyrene. Lids do not have a corner notch on the A1 corner and does not need to be oriented in any particular direction to be placed on Corning plates. Lid has a shorter skirt than standard lids. Lids do not fit Corning 2µL 1536 well microplates. Sterilized by gamma radiation.