I use these for fetch with my dog. One ball typically lasts a few weeks of 30 minutes every day. I've had one ball break in the first day it was used, but overall they hold up a lot better than some other brands that I've tried, and my dog chews them a LOT during fetch (but we keep tennis balls put away unless we're actively playing fetch - they're not left out as regular chew toys).
Rating: [5 of 5 Stars!]