Product selling points： ACCURACY: Each level has an integrated bubble level for precise measurement and the Reference Level has a magnetic bottom for added stability VERSATILITY: Adjustable barrel clamp level fits around even the largest diameter barrels, including shotguns DURABLE: Precision machined aluminum with an anodized finish NON-DESTRUCTIVE: Barrel Clamp Level features non-marring pads to ensure no damage is done at the contact points Features: - precision tool for scope reticle alignment factory calibrated reference level - maximize accuracy potential tunable barrel clamp level - CNC machined aluminum level housings protective storage case. Instructions Precision mounting and alignment of your system's scope is critical to realizing the accuracy. The professional reticle leveling system is a precision tool and technique designed to allow a scope to be perfectly leveled on any firearm with ease. The barrel clamp level is attached to the guns barrel while the smaller reference level is placed on scope base, bottom half of a ring or other flat surface perpendicular to the vertical axis of the gun. The gun is then rotated until the reference level is aligned. The tuning adjustment knob on the barrel clamp level is then turned until its level is centered to match the reference level. At this point the barrel clamp level is calibrated to the guns axis. The scope can be installed loosely and the reference level placed on top of the scopes turret cap. The scope is rotated until the reference level is aligned with the barrel clamp level and then simply secured in place. The most effective instrument available for precision scope alignment.