Multi-Function: Designed for Reflector telescope; fit for standard 1.25 inch diameter; this sturdy laser unit allows to swiftly and precisely collimate Newtonian telescope; accurate collimation in a few minutes provide more clearer image Premium metal construction and anodizing aluminium processfor long time use; require one CR2032 lithium battery 【Battery is not Included】 Practical Design: Red laser collimation beam with 7 brightness levels; wavelength 635-655 nm; output power: less than 5mw; much safer for your eyes; only when the optics have been accurately collimated can the telescope offer you its full performance Well-Engineered: The laser comes fully adjusted however further adjust if required; it has three openings for adjustment; arranged at 120°; which are initially sealed; small screw cap at the rear of the laser must be first unscrewed to allow this Friendly to Everyone: This adjustment tool can be used in all 1.25 inch focusers; provide with precise instructions in German and English about how to adjust Newtonian telescope using this laser unit; simple to get optimum performance out of telescope