I have a weak left knee, everytime I fell down on it and felt it grinding in the rough snow I hated myself for doing this to my body. I told myself I wouldn't go out again without knee pads, so I did a little research and bought these here. After trying them on I couldn't be any happier. I put them on over my first layer, and completely forget I have them on until I fall on my knees and to my pleasant surprise, no pain! It's feels like you fell on some pillows. I'm about 5"11, 165lb and I bought medium they fit great. If you are at all worried about your knees, I highly recommend them, it was worth every penny!