Because they're made of hard plastic, they don't mold round the knee, because of this no matter how hard you do them up they tend to slip. When you do tighten them up they rip into the back of your leg. They're hard & smooth, so they turn into sledges when you're on a hill, they offer sweet FA grip. 3 stars have to go for protection though, tough as old boots these, if you can modify the comfort then they'd be a 4.