The simple, clean design of the Segway Reticle Leveler makes it the best anti-cant device on the market. The MK-III works with rifles, shotguns and handguns and it mounts in a snap. Here's how it works: the plastic squares go on either side of your scope. Each square is double-sided with narrower lines on the reverse side to accommodate different vision preferences, so choose the side that works best for you. Next, just adjust and re-position your scope to align your reticle's crosshairs with the black lines on the leveler and that's it…you're ready to shoot! No more guessing, no more frustration, and no more hassle.