works as expected, great price / performance

- Close to the surface, of course, not to be used while snorkeling, since a reddish occurs (obviously), but that's not a problem as the filter can be easily taken down and then "hangs" on the string at the Gopro.
-> Fast uncomplicated installation / dismounting is in my opinion the biggest advantage over other manufacturers. (Works even under water problem.

Of course there are far better filters, but for many times the price.

+ Can not fault it, highly recommended