Carl Zeiss Jena offered various eyepieces. But the types are only classical: huygenian and orthoscopic eyepieces had been built for the Telementor. No such new types like plossls or widefields. And these eyepieces has 24.5mm or 0.96 inches in diameter. The most simplest eyepiece-type is the huygenian: It is the type with only two lenses. The focal lengths are 63mm, 40mm, 25mm and 16mm. These are eyepiece, who are good usable for longer focal length systems (f12 - f/20), for sun-observing and solar-projection. Because (solar projection) they are not pasted (and for this you need - because of the enormous heat - not cemented lense-elements!). And, my opinion: These eyepieces are good! For usage in the low and middle magnification range (~ 70 x), they are conveniant and you get nice sights with your telescope. For sure, the most huygenian - eyepieces are cheap ones, but not these from Zeiss-Jena! With these you get nearly edgesharp and clear views.         Of course, better are the orthoscopic eyepieces. Using them, you will get a sharp and high-contrast view, also in higher magnification-ranges. But there is a problem: As the eyepieces would no more be produced, they are very rare and difficult to get. And you (particularly in the U.S.) have to pay absurd and exorbitant prices for these eyepieces. There are these focal lengths: 40mm, 25mm, 16mm, 10mm, 8mm, 6mm and 4mm. So they are for use in all magnification ranges.