The Tele Vue DIOPTRX Adapter allows users to change out the smaller eyecups on their Nagler Type-6 eyepieces to a larger size, thus enabling the use of DIOPTRX-series astigmatism correctors. A new larger fold-down rubber eyecup is supplied so the eyepiece can be comfortably used without the DIOPTRX installed. The adapter installs easily with three set screws, so no permanent modification to the eyepiece is required to allow you to return it to its original state at a later date.