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. Also made for spotting scopes.