The laser comes fully adjusted; It can be further adjusted if required; It has three openings for adjustment: arranged at 120 degree which are initially sealed; The battery can be exchanged by unscrewing the small screw cap at the rear of the laser | This adjustment tool can be used in all 1.25 inch focusers; We provide you with precise instructions in German and English with a step by step explanation of how to adjust a telescope using this laser unit; Even if you are a newcomer to amateur astronomy | The laser unit has a front opening from which the laser beam can be emitted; It has a side window allowing a disk oriented at 45 degree with a central hole to be viewed; This can be later be used to see whether the laser is reflected back on itself | Built with metal material; CR2032 Lithium Cell battery which is Not include; Accurate collimation in a few minutes provide a more clearer image; The telescope can be collimated by just one person | Designed for Reflector telescope; Red laser collimation beam with 7 brightness levels; wavelength 635 to 655 nm; Output power less than 5 mw; This sturdy laser unit allows you to swiftly and precisely collimate your telescope