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. Fast, flip-open design keeps your eye on the target. Silent spring hinges won't spook game. Water-tight, custom fit friction mounts anchor them to your scope. Air-tight semi-O-ring keeps out dust and moisture. Tested to - 40AdegF. Truly ambidextrous. Weigh less than an ounce.