I just got these US Optics rings and much to my suprise the rear ring has two threaded holes. I called US Optics and they said that they are to mount a bubble level. However, they do not make a bubble level to mount on ring. I would much prefer to mount bubble to bottom of ring it I can find such a level.
The rings are very nice and of higher quality as far as I can tell from some other rings I have used, US Optics customer service was very helpful. I ordered these rings yesterday and they arrive at Fed Ex facility for me to pick up at 7:14 am this morning. I might mention they are in CA and I am in SC. Shipping cost was very reasonalbe considering item was going coast to coast.
Photo of rings installed.
