This premium .25" Barlow lens will give all of your .25" telescope eyepieces a power-doubling magnification boost with amazing image quality. The High-Power .25" 2x 4-Element Barlow Lens provides superior performance compared to standard Barlow lenses thanks to its deluxe features and 4-element design which minimizes chromatic and spherical aberrations while preserving image sharpness and contrast. As its name implies, the High-Power 2x Barlow doubles the magnifying power of any .25" eyepiece, essentially dividing the eyepiece's focal length by a factor of 2. For example: using a 25mm eyepiece in the High-Power 2x Barlow provides the same magnification you'd normally get from a 2.5mm eyepiece (25 / 2 = 2.5). Using this simple formula, you can easily determine how each of your .25" telescope eyepieces will perform when inserted in the High-Power 2x 4-Element Barlow Lens. A 20mm ocular will behave like a mm eyepiece; a mm eyepiece will provide the magnification of a mm eyepiece, and so on. Since the High-Power 2x Barlow features a sophisticated, 4-element, fully multi-coated lens design, it will provide better color correction and less distortion than 2- or -element Barlows. This means your power-boosted observations will be optimized in regards to sharpness, clarity, and brightness for a great viewing experience. View contrast is maximized thanks to a blackened interior and blackened lens edges which eliminate internal glare and off-axis reflections. A non-marring brass compression ring inside the High-Power 2x Barlow helps keep any inserted .25" eyepiece free of scratches and thumbscrew gouges. A stylish rubber grip exterior provides a sure grip, and the .25" barrel features a safety recess to keep the Barlow Lens from falling out of a focuser or diagonal should the retaining thumbscrew become loose during stargazing sessions. The Barlow's .25" barrel is conveniently threaded for use with .25" filters.