Seems rather girthy for all. I'd get one if they had something closer to 1" 1-1/4". I was gonna get it for my GF, but she thought it looked too big. Would like something smaller like Lelo Liv sized, which also might work anally too.
I really hope they make a slimmer version of it. I want to try this one but it seems too girthy for me. I think I did hear that later this year, they'll sell 1-2 other versions similar to the Stronic Eins. I can't remember where I read that, I'm not really sure how true it is.
I think part of the issue with size is the mechanics involved. Because of the motor/mechanism, it has to be a certain size to do what it's supposed to do. That will likely change as research and development on it continues to improve, I'd imagine. It would be nice to have some size options though, especially for those who aren't comfortable using a toy of 1.75" girth.
The Zwei (the prostate one) isn't thinner than the Eins. At least...I don't think it is. I'm not used to reading the specs on Fun Factory's site. But if I'm reading it right, it's not. Neither is the Drei, the textured G-spot one. Neither one is available for sale yet, but looks like you can pre-order them directly from Fun Factory if you live in Europe.