X1 UV (Ultra Violet) FILTER: The X1 UV features 4-layers of our state-of-the-art and uniformly applied MRC with Nano, which means less flaring and ghosting that you’d normally see with uncoated protection filters. Our modern coating chambers are air tight, producing a uniform coating visible to the human eye when holding the filter at a right angle to a direct light source. | MRC4 WITH NANO CONSTRUCTION | ELIMINATES VIGNETTING: The X1 features a 3.5mm ultra-slim double-threaded frame profile to eliminate vignetting on wide-angle full-frame setups. In our lab tests, 4.2mm was the frame width at which point 1-stop of light falloff (vignetting) became visible on images with 18mm wide-angle setups on full-frame cameras. | X1 UV 43mm FITMENT: The X1 UV has front-threads, which means it’s compatible with all your existing filters (for stacking) and lens caps. To ensure the lettering on the filter never wears off we laser engrave text into each aluminum frame rather than use paint-based lettering. | 25 YEARS SUPPORT: We laser engrave each X1 UV with a unique serial number. When you activate your 25 Year Ironclad Guarantee online we associate your X1 serial number to you, so any future discussions regarding your X1 UV are tracked, issues recorded, all of which goes directly into our design and prototyping pipeline.