The Tiffen 138 mm Clear filter is a wise investment. It helps protect your valuable investment from dust, moisture and scratches, which can lead to costly repairs. If desired, it can be left on the lens permanently for continuous protection.nnTiffen's ColorCore glass is produced by a process that permanently laminates the filter material between two pieces of flat ground optical glass with tolerances of one ten-thousandth of an inch, then mounted in precision aluminium rings.nnBenefitsnn- General protective filter that has no colour effect on imagesnnSuperior qualitynn- Superior quality and design make Tiffen the preferred choice of filmmakers, professional photographers and even NASAn- Tiffen has also received an Emmy from the Academy of Television Arts and Sciences for engineering excellencennSpecifications