From the makers of BarrelCool, we present "eyeBlinder" , for sale on our website: http://barrelcool.com/product/eyeblinder/ eyeBlinder is a device used to block the weak eye while using riflescopes. This is perfect for people with cross dominant eyes and will help the regular shooter by blocking the weak eye, allowing one to focus on the target in the scope and minimize eye fatigue. eyeBlinder is slim, durable, easy to use and will fit in any rifle bag. eyeBlinder is made from plastic which will not damage your scope. We have 40, 43, and 46mm scope options available. Just measure your eyepiece outer diameter and order yours today!