This Pulsar brand replacement magnetic rubber eyecup for Pulsar Thermion and Digex scopes is the same eyecup that ships with these optics from the factory. The eyecup is meant to provide the correct eye relief for Thermion and Digex series to prevent splashback from the display at night. It is compatible with all Thermions, including XM, XQ, XP, XG models and the Digex series of scopes as well.