The 50 BMG Red Laser Boresight from Osprey Global features brass construction and is activated when the bolt is slowly closed down on the rifle. The precision-calibrated laser dot is projected down the barrel and gets within 1.5" of the center. The laser wavelength is 635-655nm and the laser beam is < 5 mW. The dot size is 1.5" at 100 yards and the sighting range is 10-75 yards.