Please read the manual carefully before you use this laser bore sighter. Here is the simple step for using this laser bore sighter: 1.Select the proper adapter and find the largest diameter adapter that will fix in the muzzle of your firearm. 2.Screw the adapter into the small end of the laser emitter using the small screw in the center if the adapter. 3. When you turn the laser on, a small red/green laser dot will be emitted. And then you can adjust your scope?s wind age and elevation so that your cross hair aim at the red dot. Specifications: -Power: <5mW Laser :Class IIIa -T6061 High class aluminum alloy in beautiful black matte -8 bore adjustable adapters to fit all .177-.50 caliber -Screws already are set in the factory when center aligning. -For any 0.177 to 0.50 handguns, rifles, sights and rifle scopes - More convenient and accurate than scope and sight alignment. Easy to Use! - Battery: 1pcs CR2(14250 or 15270) - Length: 180mm, Head Dia: 17mm, Tail Dia: 4mm Package: 1 x Laser Bore Sighter 1 x Screwdriver 1 x Allen Key 16 x Adjustable Adapter Tips 1 x battery 1 x manual 1 x Exquisite Storage Box