The balls we use are regular exercise/Pilates balls: 45-75cm. They usually run between $10-25, and can be purchased from any retailer that sells exercise equipment; in sporting goods stores or in the exercise departments of Walmart, Target, or Kmart. The “anti-burst” balls are a thicker vinyl, and seem to last a bit longer, but are also a bit more expensive.
The ball should be tall enough to hit your dog right across his chest or at shoulder level. Measure where your dog’s shoulder is, in relation to the size ball. Here’s a general guide to help you in selecting the correct size:
21.5″ = 75 cm (Giant Breeds)
19.1″ = 65 cm (Large Breeds)
17.5″ = 55 cm (Medium Breeds)
15.5″ = 45 cm (Small Breeds)
13″ and under = 35 cm (Toy Breeds) use kid’s play balls from the toy section of any retailer.