I have a large waist (47') and this fit's perfectly! I was worried it would roll up and it doesn't! It does push the whole thing up a bit when you sit down, but it still sits on your back. My back hurts after leaning forward to long (like when working on the sewing machine which I have been doing lately) and this helps it.. it doesn't cure it, but it helps. I can go an hour without much pain now, not great, but better than before!