Are you sure you want to use a polarizer with that lens? CPLs won't polarize uniformly across the FoV of an ultrawide. Could be fine at 35mm, but probably unacceptable at much below about 24mm.
This is the important point, and it’s not a function of the filter, whether circular or linear, or whichever manufacturer. It’s because the polarisation of sunlight in the sky varies, being minimal at 0 and 180 degrees to the sun, and maximal at 90 and 270 degrees. So any ultra wide view will take in a wide variation in polarisation, and so the effect in terms of darkening and saturating a blue sky will vary across the image, and this will look very unnatural in your image. It is also nearly impossible to rectify in post. If you need the polariser to increase saturation in vegetation, or to control reflections on water or shiny surfaces, that’s less affected by angle of view. For such images, if you have blue sky, take one image with and one without the polariser to see the difference, plus possibly blend the exposures to have a natural sky. It’s even worse in panoramas of course.
I use Hoya Pro1 CPLs and find them very good.
