This Tele Vue DIOPTRX Adapter converts the 24mm and 19mm Panoptic and the 20m Nagler Type-5 eyepiece to a larger eyeguard size, allowing DIOPTRX-series astigmatism correctors to be installed. Note that these eyepieces have shorter eye relief than others recommended for DIOPTRX, so to minimize any vignetting, it's best to use these for deep-sky applications where your eye pupil is large.
The DIOPTRIX astigmatism correcting lens allows those with astigmatic vision to enjoy the sharpest viewing experience they've ever had, without using their glasses.