The LensCoat Lens Cover for Canon 100mm f/2.8 L Macro IS Autofocus (Black) is a 100% closed-cell neoprene coat that protects the lens from bumps and scratches. Clear plastic windows over the auto focus and focus limiter switch and also the distance scale. Ideal for nature and outdoor photographers and for sports shooters and photojournalists. The cover helps break up the shape of the lens, making it less noticeable to wildlife and more comfortable to hold. It also provides a thermal barrier, protecting your hands from cold lenses in lower temperatures. The cover is waterproof, providing protection in inclement weather.