I play "Fetch" with my dogs to give them exercise during Montana's long cold winters. Problem is, tennis balls are as hard as a rock in below freezing temperatures. I have tried several types of rubber balls. Soft foam rubber that stays flexible in the cold is not durable. I stumbled upon a can of balls for Racquetball and they are the best thing I have found yet. Karen put one in the freezer for three hours and it was still flexible. I could throw it for the dogs with no fear of breaking teeth. I left one in Blackie's kennel overnight and it was in one piece the next day.
I have had surgery on one shoulder and injured the other. I cannot throw worth a darn and a racquetball racquet is just the ticket for launching a ball out through the woods. The balls come in orange and yellow, but our local Walmart only has blue. I'll have to get some brighter colored ones for next winter.