For sealing of polypropylene and polystyrene plates, these cap mats provide an efficient seal with minimum protrusion into each well. Pierceable to hypodermic needles and self-closing. Use for chemical and compound storage to prevent evaporation and dust. Silicone pre-slit well caps permit a pipet tip or probe to enter the well without damage to the cap. Can be used at temperatures down to -80°C (except Silicone cap, Cat.No 82-276011, -20°C).