With no one selling hockey gear in North Carolina (big surprise there) I had to purchase all my equipment online. Thus I didn't have any clue what size I would be in anything, so I purchased a medium, large and extra large shin guard. The large is the one I kept.
I'm 5'4", so I'm not that tall. The extra large were way too long for me, and the edge of it kept ramming into my ankle. The large is the perfect size for someone of my height, as it safely covers the knee down to the shin, and does not get in the way of my ankle or sneakers, so it does not impair my running.
They are made of pretty sturdy material and I have already taken a few shots and slashes to them and not felt a thing, though they definitely scuff easily.