Not as durable as I would like

Of the 3 stress balls received, one popped open with 3 hours of use. My students have special needs and they types of tools are great and I was excited to try them seeing that they were marketed as very durable. Unfortunately, one got a small hole and the inside began coming out in just a few hours of use. They students were not being overly aggressive either. I' hoping the other two last longer.

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