Astromania 1.25" Telescope Eyepiece Parfocal Rings, Set of Three Eliminate the need to make focus adjustments when changing telescope eyepieces. They are made of precision machined aluminium with black anodizing. With parfocal ring equipped telescope eyepieces you can change magnifications quickly and easily. This set of 3 Astromania Parfocal Rings lets you make a set of non-parfocal 1.25" telescope eyepieces parfocal for more efficient observing. Also useful for setting focus point of calibration eyepiece used for focusing an imaging or guide camera.