This silicone-made smart little tool protects your tips from humidity, and helps to keep the hardness of the tips in a stable level. The reason that the tips become harder is that the moist chalk powder keeps transferring humidity to the dry tip while it is stored in a cue case. By blocking the tips from outside air, it can prevent the humidity delivered to the tips, and players can always rely on the same hardness of tip to improve ability.
Furthermore, your cue case will always be clean.