1.25'' 2x Magnification Achromatic Barlow Lens Metal for Telescope Eyepieces Astronomy DC622 This Barlow features an air-spaced, three-element, Apo design with fully multicoated optics. The housing is precision machined from aluminum stock and black anodized to a hard finish. The lens edges and inner barrel are blackened to provide maximum contrast. The Barlow body includes a safety undercut on the lower barrel and a brass compression ring so that your eyepiece barrels are not marred by the captive set screw.