Yes it is level that you mount on your scope. You mount this on your rifle and it helps keep you from canting your rifle to the right or left. works really well on stocks that don't have a wide forend
The anti-cant device, which is nothing but a bubble level, it tells you if your rifle is leaning (canting) to the left or right so your point of impact remains the same because your "point of aim is consistant."
When you cant the rifle to the left for example, the farther the degree of cant, the farther the bullet will impact low and left.
The angle of the bore in relation the LOS is still the same but, the bore angle is no longer just vertical, it now has a horizontal component and if canted 90 degrees it is all horizontal.
The more you cant the rifle the more you are actually removing the vertical correction to compensate for bullet drop while imparting more horizontal correction at the same time.
assuming you're going to get into distance, its a worthwhile investment if you ask me, especially when you find out how much you really are canting the gun and dont realize it. if i remember, mine was 32 and some pennies from sinclair. shouldnt take much sofa checking to get the $$$ for it. like dave said though, money for parts flows like water around here. i went broke months ago and somehow am still buying more guns and parts. theres some evil men around here.....