Arken Optics 30mm Anti Cant Scope Bubble Level

Cant is the error you never see. Roll the rifle a few degrees off vertical and the bullet walks sideways, and the further out the target sits the more it costs you. This level clamps onto a 30mm scope tube and puts the bubble right where a glance catches it before the shot breaks.

The body is CNC machined aluminum, so the weight added to the rifle is negligible. A center point marker in the vial gives you one reference to line up instead of splitting the gap between two hash marks. It clamps on with the scope still in the rings.