The latest iPhones are very capable cameras. We have already covered a bunch of iPhone lenses and rigs that let you capture better quality photos and videos. SANDMARC Hybrid Filters are also worth a look. They are made with multi-coated and anti-reflective glass for better color accuracy.
The Hybrid Filter combines a polarizer & ND filter to reduce glares and reflections and give you more flexibility with shutter speed. The Hybrid Filter lets you capture clear photos of skis and transparent bodies of water. It is compatible with other SANDMARC lenses and iPhone XS Max to iPhone SE (in addition to Samsung Galaxy and Google Pixel devices).[where to get it]