The Proviz Classic waterproof helmet cover is adjustable and designed to fit over all standard size cycling helmets. It is made from fully waterproof polyester waterproof material and is seam-sealed so not a drop of water will get in. It is elasticated round the edges which can be adjusted to ensure a secure fitting around your particular helmet model and the reflective detail helps to ensure your position on the road is more easily seen at night. It is perfect for commuting in wet winter weather.