K&F Concept are now my go to manufacturer when I need a filter, be it for camera, action camera or phone, I just know they will perform and be manufactured to exact tolerances, this being no exception.

As a photographer and videographer I spend a lot of time switching between equipment, if we exclude high end stuff like Arri and specialist stuff like Drones and Action cameras, I have settled on Fuji and Sony for my portable kit alongside the iPhone which is now good enough for a lot of my paid work.
The issue is that having this selection means different lenses and different filtersizes, so, to deal with this , I have settled on 67mm as that is native to all my phone cases and rigs and easily adapted to camera lenses by printing a step up.down ring as needed.

Hence ordering this as it will spend a lot of time on my phone - pictured - in fact probably 90% of its life will be my using it this way.

But surely it is expensive for a phone filter?
I would argue it isn't, as mentioned earlier, the iPhone is now a very capable imaging device and this definitely enhances the experience, a CPL is always a must have, but so is a Black Mist to take some of the harshness out of images/video and give it a softer more cinematic feel, having them combined in a single filter is perfect.

It is light, so no detriment to the handling of the phone and still gimbal friendly, even with a cage as opposed to the case picture.

Optical quality is excellent, in my usage so far I have had no need to correct for vignetting at the edges or other aberrations, something that I have had experience of with cheaper filters, and handling it is a delight, with a smooth action and no tendency to lock itself solid to the device it's attached to due to well honed threads.

Of course I recommend this!!