Good price / quality ratio 638

This UV filter may be simply a piece of glass, but it is decent quality and effectively protect your valuable optical scratches, shocks and other particles that could damage during your photographic adventures.
Its relatively thick ring risk, in absolute terms, to create large aperture vignetting. But this problem really lay with a goal "ultra wide angle."
A 18mm on APS-C, I did not notice anything catastrophic.
The only real issue to consider is the treatment "anti reflection" of the filter that is not highly effective. It can play tricks by generating halos and flares unsightly when you directly will photograph the light sources (lamps, signs, etc.).