David Backcountrywrote a review of Castelli Upf 50+ Light Knee Sleeves on October 19, 2017
Familiarity: I've used it once or twice and have initial impressions
I've worn these ~2 times. It's been hot both days, but they didn't feel any hotter than riding without them. I was most worried about size. I'm 5'11", ~150lbs. My thighs are 21.5" around, my calves ~15". I'm a Large and they fit great. I wear about a 32/32 in pants. They've ridden down about 1 inch over the course of a 50 mile ride, but I think they'll be fine if I wear them under my shorts instead; they've got grippers on both sides, so they can be worn over or under shorts.