The Binocular Doubler gives you a 2x boost to the magnification of any full-size Vortex binoculars, so you can take in views similar to those you'd expect to see through a spotting scope. The Doubler fits comfortably in your pocket or pack and easily slips over the one of your bino's eyecups. It has the same kind of high-grade glass that's in Vortex binoculars - plus fully multicoated lenses, textured grip surfaces. Simply slip it onto the outside of the eyecup and enjoy a nice boost in magnification. 2x magnification boost Twist-up eyecups Also works on Vortex Recon R/T & Recon Mountain scopes DOES NOT work on Vortex Fury & Kaibab binoc Mfg: Vortex Optics