I found that the best way to keep condensation, fog etc. off scope is NOT TO COVER(SEAL) GLASS PERIOD!! I carry a small piece of COTTON CLOTH(like a cut piece from a T shirt) in my pocket to wipe any snow, water that collects on glass. I tried Butler Creek caps, rubber bikini style and whut have ya. I came to the conclusion many moons ago...nothing works best!! For NON-RainGuarded scopes...i use Scope Dope which is a lense paste that is friendly to coated optics. Its now available in a spray. Many professional guides swear by Scope Dope.
I also found that the Butler Creeks extension over frt/rear objective also tends to reduce light transmission which is especially noticed in low lite conditions.
Only reason I ever cover glass if gun is exposed to extreme dust/dirt/grime conditions where i wanna protect glass...which is very rare.
I wont go out in harsh weather without the butlers on. I have a pair on 4 of my rifles. It only takes a fraction of a second to flip those caps up during harsh conditions when something is coming your way. It rained where i hunted this year on the first day and my dad didnt have scope covers on his gun so he had to use a hankerchief. That didnt work out so well for him. I ended up breaking down and buying him a set. He was happy as all get out. I was wondering, if butler creek made those caps in camo?