Butler Creek Blizzard Flip-Open Size 9 Scope Cover

I've used these...

I've used these Blizzard scope covers for about 20 years now. I once missed an opportunity to shoot an elk because the objective lens was covered in rain drops, with no time to wipe it clear while there was still a shot. These ones protect the scope from weather and debris until flipping open just prior to the shot. And when and unexpected close up shot presents itself with no time to flip the cover up, I can see right through well enough so I don't miss the opportunity. This is the only product I know of that protects the optics for longer shots but still are see-through to allow for a quick shot when necessary. Only downside is that if fit is not good, they 'll either slip off or pop open. I lost the ocular lens cover somewhere in the sagebrush crawling toward an antelope, but fortunately the objective lens cover, the one that really matters if you normally carry your rifle with a sling and the barrel pointing up, was a perfect fit and is not going anywhere.