I ordered the K&F Concept premium lens guard for my Insta360 X5 and found it pretty good on the whole. The tempered optical glass feels robust, and the 9H hardness gives me confidence it can take a few knocks without scratching.It was easy to attach via the bayonet mount. For a few seconds I saw a reflection from the lens guard, then it went away, so clearly the camera adjusted itself automatically.
The twist-lock mechanism is well designed and holds securely, even during more active filming. I also appreciate that the microphone cut-out keeps audio unaffected.

Image quality is excellent in video, and I’ve not noticed any loss of sharpness or clarity, but the couple of still images I tried were rather soft. I have only had the X5 for a short while, so perhaps I need to change something in the settings here. 

The multi-layer coating really helps with smudges and fingerprints, and cleaning it is quick and easy. Overall, this feels like a well-made, purpose-built accessory that offers proper protection without compromising performance.On a side note, I was glad to see the rubber hood still fits over the top with this lens guard in place.