The surface tension provided by the circle drawn with the pen ensures that only the amount of antibody solution needed for sufficient reaction will be applied. Stable up to 129 degrees C in microwave heat. The Pap Pen is very effective for immunostaining procedures by the Peroxidase-Antiperoxidase (PAP) method, ABC method, B-SA method, immunofluorescence method, ASD method, Enzyme method and Frozen Section method.