This Tennis Ball Hopper stands out as the best ball box I've used so far. Its metal structure frame comes with springs, making it easy to fold and unfold, while providing strong support for the ball box. The hopper can hold around 100 tennis balls and features a zippered net, allowing secure transport without balls spilling when separated from the frame. The wheels at the base roll smoothly for easy movement, and they can be locked when you need the hopper to stay in place. It’s lightweight yet highly functional, making it a highly satisfying product.