I wear this.

The shell is flexible. I removed the chin strap gear. It's not certified but it is "safer" in my opinion. It is easier to slide on your hat and cleats with this. It is very compliant. In the winter I tape the ears and top holes. It's kind of hot (gotta soak the head) but then it also protects from sunburn. And the partial wind and bugs. I usually modify my hats to give me a very snug, comfy fit. With this I tied up the apex (I have a pointy head) and I shaved the mullet area with a razor and pointy stick, so it wasn't all over the back of my neck.

There are other versions. This one is heavily padded in the back of the head. Which makes it hotter in this spot.

It weighs in the 500 gram range I think. A little heavier. But the center of gravity is lower.

I can not attest to the efficacy of any helmet but this one.