LensCoatA(R) for the Canon 17-40 f/4 LensCoatA(R) telephoto lens covers offers your valuable equipment some protection from scrapes and bumps, preserving its resale value. The LensCoat also acts as a thermal barrier making the lens more comfortable to handle in both hot and cold temperatures. The LensCoatA(R) Canon 17-40 f/4 features a clear plastic windows over the distance scale and a cut out for access to the auto focus control.