Ball Savers are a pretty nifty device designed to extend tennis balls' lifespan by storing them in a pressurised container.   To that end they do work. Certainly versus storing them in your tennis bag. They can help balls retain their bounce for much longer although they won’t feel like brand new.  What they can’t help with is restoring worn felt or removing dirt and moisture that can slow your balls down.  But they’re definitely worth a try if you have the patience to use them. We recommend the Gexco Tennis Ball Saver with its retro styling.