As you can see in the picture, the Televue dioptrix fits on the shadowqest/nighthunter okular.
The dioptrix fits perfectly and does not fall off when you hold the binoculars upside down.
Note: my (left) eye is -4.5 and I can just focus at infinity.
The wing eyeguard can be rotated.
Dioptrix makes the eyepiece wider,... less space for your nose.