Vortex 34mm Bubble Level

VORTEX RIFLESCOPE BUBBLE LEVEL FOR 34 MM TUBE Model BL34 The Vortex bubble level helps for the most precise long-range shooting. You can easily see the bubble level while on the rifle to ensure that the rifle is perfectly vertical. This will eliminate potential error caused by shooting a canted rifle. This comes into play increasingly as distances get further. The unit mounts quickly and easily to the riflescope tube without any specialty tools.