Conventional tennis ball containers are notoriously non-recyclable since they are made of plastic and aluminum and need to be sealed at 14 psi. After tennis balls are removed, they immediately start to lose their internal pressure and won't have the same bounce; thus, they need to be replaced more often. Re:serve addresses these problems. It is made out of recycled tire tubes and can easily be repressurized. Since it is a standard schrader valve, one only needs a bike pump to store  tennis balls at ideal pressure.
The result is a more environmentally friendly package and balls that last longer!