LensCoatA(R) for the Sigma 500mm f/5.6 DG DN OS Sports LensCoatA(R) Sigma 500 telephoto lens cover 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 LensCoatA(R) Sigma 500 features a clear plastic windows over the AF / OS controls and also the distance scale.