Made from high-quality materials. Precisely built. It offered the least amount of resistance I've had screwing on a new filter. It's very thin so it won't interfere with wide-angle lenses (as much as is possible).

Using a full-frame DSLR, I did side-by-side, pixel-level comparisons between shots with no filter and with this. One photo was a wide-angle shot the included sky on a high-UV day.

Results: well, I didn't see any difference in color or richness in the high-UV shot, so I wouldn't buy it just for that. Mostly, people buy these simply as lens protectors (and trust me, they've saved my bacon on a high-end lenses several times now!). As a lens protector, you want it to be as unobtrusive as possible and I am pleased to report that I can detect no significant difference with any test shot - color balance, sharpness, contrast - they all are so close that I could never say definitively that any minuscule difference was due to the filter.

A very high-quality product with (presumably) a good level of protection. The packaging and case also convey a feeling of quality and pride in their product.