Before I purchased this product, I researched extensively for the best exercise ball. I needed a sturdy ball that would last for a long time and not leak profusely. I had terrible experiences with balls that smelled like toxic chemicals and would lose its air after a couple of uses. This ball had great reviews, and also it's initial purpose was for physical therapy. This was refreshing to know before purchasing. I purchased the pink 55cm one; it comes in 55cm, 65 cm, and 75 cm. I'm 5'3 so I thought 55cm would be the perfect height, and indeed it was. When I received my product from Amazon, I inflated to "almost capacity" due to a suggestion from a friend. This was true because after I let it sit for a day, it was at a perfect capacity. After using this ball for a month now, I realized that this is the best ball I've ever used. It's sturdy, and hasn't leaked yet. I would highly recommend this to anyone doing any type of exercise.