You would think a decent dog ball for a couple of small Jack Russell terriers would easy to find, but it's not.
Most of the toys and balls sold at Pet Stores are massively expensive veterinary bills waiting to happen.
Tennis balls will last a while, but how many "escape" around the house and are eventually found inside the dog at the veterinarian's office? A lot!
Kongs are OK for some dogs, but they do not flex enough for a small dog, and the result is that small dogs get tired of them pretty quickly.
Of all the dog balls in the world, my dogs like balls with squeakers in them the best, and I have a number of those that have stood the test of time pretty well.
That said, these small hard squeakerless balls are very popular too, as they fit inside a Jack Russell's mouth pretty well, but are still too large too swallow, and they bounce like crazy.
There is just enough flex in these balls for the dogs to "get their chew on," but they are just hard enough to survive the experience.
Of course, I do not leave balls with any dog -- one reason I have never had to have abdominal ball surgery on any dog.
One last tip: stay away from antlers. I heard a lady asking about those at the pet store, and the pet store guy said that antlers do not splinter. True enough, but while the antlers themselves may not splinter, they are hard enough to splinter dog teeth, and that should be of major concern to every dog owner.
A final note. These two balls are for small (10 and 12 pound) Jack Russells. If you have a larger dog, get the right ball or chew toy for that animal. For Lucy, the big dog that is often at the house, that turns out to be a Galileo Bone.