As we know, lenses are valuable items, and even a small scratch can mar them forever. So in order to protect it, you need a lens filter cap! What you are viewing is a Mennon 37mm Portable White Balance Lens Filter Cap with Mount WB, which is a professional lens filter cap for all 37mm size lens well, and can be used for white balance measurement and as a lens filter cap! The 37mm lens cap keeps a spare cap in your gear bag for the inevitable lost lens cap, too! Pinch the sides of the white balance lens cap and snap it into place-it fits securely and your lenses are covered. Whether your hand are tender or coarse, the lens filter cap will take on or off easily when you using the hood. Give your camera best care, you should get the white balance lens filter cap.