The VU Sion UV Filter is designed to be a part of your lens from
the moment they're screwed into place. Equipped with VU patented iO
Lock, which environmentally seals and protects the front element of your
lens, VU UV filters also feature hardened glass, an optimized UV
rejection coating, VU unique White Balanced Multi-Coating and a special
Flat Wave Overcoat to ensure that your images are captured exactly the
way you envision them.