these are the Cadillac. supposed to return to zero, when reinstalled. but if going on multiple uppers, you'll have to re zero each time:

http://www.midwayusa.com/product/37...h-integral-30mm-rings-flattop-ar-15-matt

i am using these:

https://www.youtube.com/watch?v=kI9VCm5kUyo

if a man speaks, and there isn't a woman around to hear him, is he still wrong?