Keeping your cylinder protected from the elements when it is not connected to a regulator is important to your safety and the reliability of your life support system. Protect your cylinder DIN valve from water, dirt, dust and crawling critters. This non-corrosive Plastic DIN Protector Cover assures proper protection. It slips over the top of your valve to protect your cylinder valve from having water enter inside the delicate internal mechanism when on the deck of the boat or when washing your gear after diving. Cap comes with a loop of line to attach to valve, so its right there when you need it. Valve cover is useful for identifying cylinders and is also the standard to let boat and dive operators know if your cylinder is full or empty. Place cap over valve when full and leave off when you need a gas fill.