Big Feet Donuts Tennis Training Aids : Ideal for working on footwork, movement, positioning, and split-step guides, Big Feet Donuts are designed to stay in place with an anti-slip and dirt-resistant construction. Each set of 6 consists of two orange, two green, and two yellow donuts that allow you to customize your training. 21-inch diameter. Great for group lessons and keeping players safe distances apart. Perfect for tennis as well as physical education classes.