I'm an avid mtb rider and sometimes push things a little too hard...if you don't go down at least once per ride, you aren't riding hard enough, right?! Well, a few weeks ago, my front tire washed out and I slid on the dirt across some rocks. This gashed my knee open substantially. I decided I was too old to be injured like this. The inconvenience of being miles from my truck and having to limp back while bleeding, then having to hop around for a few weeks with stitches, being off my bike, not being able to swim, etc.... well.... isn't fun. So, I sought out some protection so it won't happen again. I'll say that it's summer here in NC and freakin' hot but as long as you are moving, these stay fairly cool. At least as cool as knee pads can be. My thigh is around 17.5 inches in circumference a few inches above my knee and the medium fits well and stays up when I'm pedaling. The rubber grip at the top and bottom of the pad work well against the skin. There is enough padding to be protective but not too stiff so to impede cadence. For all you guys dropping off structures and cliffs, you probably need something more substantial but for me these are perfect. All in all, these met my expectations so I'm giving them 5 stars.