Exactly - & on a gun that kicks some.

I've seen them on the 3/8" eye relief Immersive scopes on non-recoiling air rifles to eliminate side light into the sight picture.
There was one on the 1-40 Immersive scope I purchased for my Condor .25., however I dislike them and took it off. I prefer not to have the rubber eye-cup.
The ocular lens cover has written on it "NON RECOILING RIFLES ONLY"