The key element of a leg cast cover is its ability to keep out moisture. Opt for one that is airtight and watertight. Most waterproof leg cast covers are made from plastic, vinyl or rubber, which are highly waterproof materials. If the quality of the waterproof leg cast cover is poor, however, you may end up compromising your recovery. If you have a sprain or fracture on your leg and need to wear a cast, you know that one of the most important rules is to keep the cast away from water. Getting the area wet can result in bacterial infections, uncomfortable itching or even allergic reactions. As a result, it’s important to use waterproof leg cast covers to ensure the cast area stays dry when you’re bathing, showering or swimming.