I have one too. As far as I can tell it’s just an extra layer of thin plastic that sits, unattached, under the expanded foam. The idea being that it slides an

I have one too. As far as I can tell it’s just an extra layer of thin plastic that sits, unattached, under the expanded foam. The idea being that it slides and stops the helmet gripping you head. I’ve often wondered, how much of the same feature would be achieved with just a cycling cap under the helmet? I’m not sure there was a huge premium for getting MIPS so I guess I’m happy to have it. It certainly doesn’t hurt.