This Butler Creek flip-up Eyepiece lens cover opens at the touch of your thumb and features a watertight friction mount and semi O ring that securely anchors the cover, sealing out dust and moisture. The ocular lens covers feature a large push button for quick spring loaded opening when you want to keep your optics protected until the perfect shot presents itself. Eyes is the ultimate scope lens protection for hunters and shooters. It is custom-fit to your scope. It creates a watertight, airtight seal, and opens with a touch of your thumbs. You'll be able to put your shot through the narrow window of opportunity in the most extreme conditions! Features Fast, flip-open design keep 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 -40 DegreeF. Truly ambidextrous. Weigh less than an ounce. Also made for spotting scopes..