This is a Butler Creek Scope Cover known as the Flip-Open, model MO30010.
Simply the ultimate scope lens protection for hunters and shooters. They're custom fit to your scope" create a watertight" airtight seal and open with a touch of your thumb" so you can put your shot through the narrow window of opportunity in the most extreme conditions.
Features:
Silent spring hinges
Water-tight
Air-tight to keep out dust and moisture
Tested to -40 degrees Fahrenheit
Truly ambidextrous
