The 
NUPROL NP Lens Shield
 is an airsoft accessory designed to protect valuable red dot sights, scopes, and optics from damage caused by incoming BBs. It mounts on standard 20mm Picatinny rails and features a convenient flip-up/down design. 
 
 
Features and Construction
Primary Function: Deflects incoming airsoft BBs to prevent damage to expensive sights and optics.
Mounting: Designed to fit on universal 20mm Picatinny rails, which are common on airsoft weapons.
Design: Features a low-profile, flip-up/down design, allowing the user to easily move the shield out of the line of sight when not needed.
Material: Constructed from a combination of metal for the mount and a transparent, impact-resistant polycarbonate shield.
Visibility: The transparent shield maintains optical clarity, ensuring an unobstructed sight picture.
Included Components: The package typically includes one NUPROL NP Lens Shield mount and two transparent shields (often one clear and one yellow-tinted for different lighting conditions) that can be swapped using an Allen key.