"I have a cap and also only a lining. Which allows me, to wear any hat above it, I like. I feel, that it helps, from radiation from above, for example when I am in my car or walking in the town with many cell towers around. Sometimes in my car I wear only the lining, which is very comfortable when it is hot outside. In my last apartment was much more radiation from the neighbors' WIFI and I slept with it most of the nights."