I already have the 4 ND filter pack by K&F Concept for my Osmo Action 4 camera, so a diffusion filter is a very welcome addition to the collection.

It comes in its own, very solid and safe plastic storage box. Installation is super simple - you just unscrew the fabric protection glass and screw this filter on instead.
The black diffusion filter is made to the same high standard as the ND ones - metal casing and multi-coated glass, protecting from water, dust, oil and any scratches. It's perfectly aligned with the camera's looks.
The effect is indeed cinematic - a slight blur to lights and shadows, which softens a sometimes unnaturally sharp and ‘edgy’ looking image. It also works great for smoothing out close portrait shots - a bit like a skin smoother filter.

I sort of disagree with one of the reviewers that it's a cheap filter. Unless they literally meant the price, which at £22 is quite attractive. This is after all an action camera more than a vlogging one, so having any filters for it is already a bonus. Definitely highly recommended.

Thank you for reading my review. I hope you found it helpful.