I am 5'3" 133 pounds. I bought the medium and it fits a little loose, but I think it is the right size. I was worried about the armor, but the looseness helps. I wasn't planning on leaving the armor in, but it's positioned perfectly and is comfy. It is very breatheable. I ride in Florida and even in the heat, it is usually a little cooling.

I am a beginner rider (three years on my own bike) so I want to be safe but stylish too! The protective padding in this is great and doesn't interfere with motions. It's very comfortable and I love the bright pink :) I ordered an XL - I'm about 5'4", 200lbs - and it fit perfectly! (And it matches my new bunny helmet cover as well haha!)