A handful of years ago, my son went down on a descent. We took him to the local walk in clinic and they looked him over with a broken collarbone diagnosis. So off to the ER we went. As we were sitting there, I asked him if his helmet hit the ground. He didn't think so. As I looked at the side of his head, I could clearly see a red waffle looking area along the side. When we got home, we looked at his helmet and sure enough, it was shattered. Without the helmet, he'd surely have had a concussion. They are not perfect, but they can be the difference between a concussion and being able to walk away.