Universal Laser Boresighter 

POWER OUTPUT: CLASS II, <1mW or Class IIIa,<5mW, WAVELENGTH: 650 nm BATTERIES: 3 - A76/LR44/AG13 BATTERY burn time: 1.5 HOURS(constant "ON"),WEIGHT: 1.3 oz. LENGTH: 6.125 in., 14.3 cm NIGHT TIME RANGE: 500 YARDS, 450 METERS No ammo waste, Push button ON/OFF switch,
The 4 adaptors are self-expandable,Its precise enough so that it is good to fit into the barrel (not shaking).

Technical specifications

Laser: Class II or Class IIIa
Power: <1mW or <5mW
Wavelength: 650 nm
Weight: 50g
Length: 143mm.
Head Diameter: 16mm
Tail Diameter: 4.5mm
T6061 High class aluminum alloy in beautiful black matte finish.
Four bore adjustable adapters to fit all .177 ~.50 caliber.
Screws are already well calibrated at the factory when center aligning
Set your firearm quickly !

Laser bore-sighting systems make it possible to zero in your firearm and check the boresight of your scope, any time anywhere, WITHOUT HAVING TO FIRE A SHOT. It is so small that your laser system can be transported easily while hunting and allows you to control the boresight of your aiming instruments, especially after a fall or after knocking the scope.Functioning: position yourself 10 to 22 m from the selected target (meeting point of the line of sight, the trajectory of the bullet and the laser beam, see diagram below). After having inserted the laser sighting system in the firearm muzzle, point the laser beam at the target, then, with the boresighting, centre your reticule on the laser dot.