The LensCoat Lens Cover for the Sigma 150-500mm Lens covers the lens with a 100% closed-cell neoprene coat, offering protection from bumps, jars and nicks. It also helps break up the shape of your lens making it less noticeable to wildlife and allowing you to blend in with your surroundings, making it ideal for nature and outdoor photographers. LensCoats are also useful for sports photographers and photojournalists who spend a lot of time exposed to the elements as they are waterproof and also provide a thermal barrier, protecting your hands from cold lenses in lower temperatures. The LensCoat Sigma 150-500 features clear plastic windows over the auto focus controls and also the distance scale. A small hole on the last segment lines up with the white dot indictor, making it easy to quickly line up your lens with camera mount even with the cover installed. They are easy to install and remove and leave no residue on the lens.