I am 175lbs standing tall at 6'2" and I wear a large.These work perfectly from 0-40F with no other leg layering. The compression is quite nice on the legs. I'm no rocket surgeon, but it sure seems like the elastic bands help with muscle fatigue. I also wore these for multiple long sweaty runs. Thankfully, this material does not bottle up that wonderfully smell. Washes out every time!Only two downsides- They are extremely difficult to get off over your ankles when you can't feel your hands and the fit around the crotch to waist area. I'm not used to wearing pants that go up to my belly button.So to conclude, BUY THESE! You won't regret anything other than the fact you didn't buy more.