105MM UV Ultra Violet Filter For SIGMA 120-300mm f/2.8, 150-600mm F5-6.3 DG OS HSM (S) Sports, Olympus 90-250mm ED Zuiko Digital Zoom, 800mm f/8.0 Mirror T-Mount Lens UV filters reduce haze and improve contrast by minimizing the amount of ultraviolet (UV) light. Especially useful in areas of high altitude or snow, eliminating the undesirable blue cast. Filters serve as a great and inexpensive lens protector. Use one at all times to protect your delicate lens from dirt, scratches and accidental damage. Better to scratch or break a UV filter than an expensive lens. 105mm Lens Thread