If you need a prescription lens in your riding glasses, theShimano Eyewear RX Clip will help keep your vision clearer. The RX-Optimal Clip transforms the standard Shimano eyewear models S71X, S60X, EQX2, S50X, S50R, S40R, S40RS and S20R into an optical dream. It allows you to fix the Clip as close as possible to the lens and therefore a perfect fit and vision is guaranteed.