Does just what you wanted it to - U.S. Optics Rail Mounted Fixed Bubble Level

I put this level on a fine bench rifle and I'm glad I did. Being mounted firm to the Picatinny rail, it makes getting the gun set-up level on the tripod very easy. Just a glance and I can see if anything has come out of adjustment. The cap that screws on to the opposite side during use is a nice touch.
Pros: Easy to use
Cons: pricey

This review was written in the old system and had content requirements that are different than reviews written today.