Does what it is supposed to. Little expensive, but if your battery goes out on your optic and you don't have a spare, well, you get the idea. I cut the tether off, snagged easily.
Pros: lightweight, easy to put on, seals nice & tight
Cons: tether on the cap gets in the way and is easily snagged
This review was written in the old system and had content requirements that are different than reviews written today.