This Leupold ScopeSmith Anti-Reflective Device has a 40mm diameter, and it snaps directly into 40mm objective Leupold scopes with no threading or adjustments required. This AR device is incredibly easy to use, and it mimics the performance of Leupold sun shades by attaching directly to the lens. The 40mm Leupold ScopeSmith Anti-Reflective Device measures _-inch deep and features a rigid plastic housing that encases a metal honeycomb design. This design serves to prevent reflection from your tactical scope