Flip-Open scope covers are 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. The fast, flip-open design with a silent hinge keeps your eye on the target and won’t spook game. It weighs less than an ounce and has been tested to -40 degrees F. The fit range is .01 under and .025 over the given measurements.