Some are, some arn't.
I got one I tossed in the trash after about 2 weeks, it wouldn't hold a zero for crap.
Then, back in the late 60s maybe early 70s my brother bought a 3X9 Banner for his Argitina mauser. He set the eye relief too far back and got a nice half moon cut over his eye. I offered to set the eye relief for him but he didn't want anything to do with it and gave me the scope.
I had just bought a Ruger 77 in 7 RM and couldn't aford a good scope so I put my brother's Banner on the rifle. That was about 40 years ago, its still on the Ruger and still holds a zero. I don't have it now as I gave it to my son but its still has the orginal Bushnell Banner and still shoots.
CPT USAR Ret
USAMU Sniper School Oct '78
Distinguished Rifle Badge 1071