Amazing!
I bought 4 of the basketballs (and 2 soccer balls) for a glow-in-the-dark activity at our Church. The kids went crazy over the glowing balls and LOVED playing with them. They are incredibly bright in the dark. We used them for 2 hours and they stayed bright. Unsure how long the batteries will last over the next number of months... but they were such a hit I've already ordered replacement batteries so we are prepared.