Compact and easy to read - B-Square Scope & Sight Tools - Bubble Level - Weaver Dovetail T1006

This little guy is nicely constructed and the bubble is easy to see. I mounted it on a scope base. One concern is depending on how low you mount your scope you might not be able to squeeze it under. I don't have that problem because of a 50mm objective bell that would bottom out on the barrel before hitting this level.

Compare this to the levels that mount to the scope instead. What are the advantages and disadvantages? Sure both your scope and your rifle should be level but if I had to choose one I choose the rifle. After mounting this and leveling the rifle I place the scope on its rings and then place a small hand level on the top turret to level the scope. Now everything is perfect.