ApexHorizon Optics Rifle Scope Bubble Level Fit 1in 30mm 34mm Riflescope Tube for Air Gun Hunting Or Long Range Shooting Centering line is spaced apart,the center pointer makes it easy and fast to focus on the bubble when shooting and hunting. It can be mounted on both sides, either left or right! Single screw design make it lighter and easier to set up on. It's full CNC machined with T6061 but not using the aluminum alloy sections.That is why we make it become the most precision scope bubble level all over the world--tolerance be controlled under 0.01mm! Whenever you are doing some precision long range shooting or shooting with your airgun, the ApexHorizon scope bubble level will ensure your rifle is perfectly vertical. It really make a difference and improve your accuracy. ApexHorizon Optics Bulletproof 100% Money Back Guarantee. We promise you always get what more than you paid here.