LensCoatA(R) for the Canon 600 f/4 with IS III LensCoatA(R) telephoto lens covers offers your valuable equipment some protection from scrapes and bumps, preserving its resale value. It also helps break up the shape of your lens, making it less noticeable to wildlife. The neoprene LensCoat acts as a thermal barrier making the lens more comfortable to handle in hot and cold tempertures. The LensCoatA(R) 600 III features a clear plastic windows over the auto focus and Image Stabilization controls, and also the distance scale. A small hole on the last segment lines up with the red dot indictor, making it easy to quickly line up your lens with camera mount even with the cover installed.