I bought two, and was skeptical about the cheap plastic pump that came with the ball, so I purchased an electric pump. The electric pump worked poorly, and the cheap plastic one ended up working just fine. Within a week, however, in some freak accidental sequence of events, my daughter had popped one. She had accidentally pulled down a shelf, which caused a glass vase to shatter into a glass frame near the ball. We vacuumed and picked up all the pieces, but a tiny shard must have remained, because when she sat on the ball (she only weighs about 90 lbs), the ball popped. The construction of the ball helped in that the air released slowly, and not dangerously, as advertised. The other ball that remained in tact is absolutely perfect however, and I use it every day.
Not sure if they sent me the wrong size, but this product is WAY too small to be used by an adult. I ordered the 55cm Jump Ball, which I was expecting to be the same size as my 55cm medicine ball, however it is approximately half the size. I think they include the handles in the overall size. I am only 5' 5", and this jump ball is way too small to be useful because I am so crouched down when I sit on it that I have no leverage. Total waste of money.
As so many said, takes a bit of time to get it to full size. But...if you fill it with the supplied pump (mine worked perfectly, no complaints!), let it sit for a few hours, put in more air, let it sit and continue to do that it will fill to it's full size within a day or so (you have to let the rubber stretch) and it's as big as they claim! We took our time and did it over two days filling it until it was taut and then letting it sit for hours.
It comes with an excellent wall hanging chart, well illustrated. I'm fairly heavy and it holds my weight well and doesn't feel like it will burst.
It's definitely a good value.
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