"I looked at several knee protectors after a bout of burstitis following over exercsion. These were the only polyurethane based pads which therefore last much longer and are tough. Gel pads using plastic bumpers might be stronger but are much more uncomfortable than this type than can fit into a pair of work trousers. Not too expensive either, by comparison."
"Probably hard enough to stop a nail, nearly as hard as kneeling on the floor. They do not stay in place. Quiet likely if you get up and down enough one time they will only be half over knee thus you twist it. great!! Then again, if you stay on your knees for a while in one place (without moving), having arranged them correctly and holding them while bending (almost impossible) they're quiet (un) comfortable. good job i'm acrobatic"