The MDT Elite Scope Rings offer a solid, lightweight mounting system for your optics. Built-in bubble level. MDT Precision Scope Rings are designed and manufactured to STANAG 4694 specification, also known as “NATO spec”. This means the scope ring sits tight to the top of the scope base rail, with pressure being applied to the underside of the angled rail surfaces to maintain a solid interface. This design also allows mounting on out-of-spec rails.