This flip-up cover protects objective of the scope. It's easy to mount, using scope's objective thread. You can set the direction where you want to open covers. This Flip-Up Cover is compatible with the following riflescopesMeoStar R2 scopes with 56mm objective lensesMeoStar R1 scopes with 56mm objective lenses Meopta MeoStar 56mm Objective Flip-Up Cover 1057365