"Give your telescope eyepieces a 2x power boost! The Shorty 1.25- inch 2x Barlow Lens doubles the power of any 1.25- inch telescope eyepiece it's used with. For about the price of a single eyepiece or less, the practical Shorty 2x Barlow effectively doubles the number of telescope eyepieces at your disposal. The Shorty 2x Barlow Lens doubles the magnifying power of any 1.25- inch eyepiece, essentially dividing the eyepiece's focal length by a factor of 2. For example: Using a 25mm eyepiece in the Shorty 2x Barlow provides the same magnification a 12.5mm eyepiece would normally exhibit (25 / 2 = 12.5). Using this simple formula, you can easily determine how each of your 1.25- inch telescope eyepieces will perform when inserted in the Shorty 2x Barlow Lens. A 20mm ocular will behave like a 10mm eyepiece; a 6mm eyepiece will provide the magnification of a 3mm eyepiece, and so on. Using the Shorty 1.25- inch 2x Barlow Lens is easy. Simply insert the Shorty 2x Barlow into your telescope's focuser or diagonal, and then insert any 1.25- inch eyepiece into the Shorty, gently securing it in place with the two thumbscrews. Then, adjust the telescope's focus wheels to enjoy double the magnification of the eyepiece used. Think of the money you can save with this practical and affordable telescope eyepiece accessory!