STC’s filters are coated with our UltraLayer technology on both sides of the lens. To protect the coatings, FIRST, use a lens blower to remove dust or other particles to prevent scratching. Hold the lens up to a light so you can see if all the particles have been removed.Once all particles are removed, then use a soft lens cloth or lens paper to remove any fingerprints or oils. WE DO NOT RECOMMEND lens cleaning pens. They accumulate dust particles (or worse sand!) over time and you are more likely to scratch the lens coating.