I'll try to keep this fairly short (like how I like to be around real Men).
I respond well to height; all the better if a Man loves his size advantage over me. If I'm not even chin-high to someone, even if I'll never meet them, it has quite an impact on me. I also respond well to alphas who carry themselves with dignity. You know, the sort who won't see me as scum, but as a lesser male who needs some guidance and training by a real Man. Someone I can look up to literally and figuratively. I may never find it, but that's a risk I'm willing to take.
Ultimately, to be collared and owned by a tall (ideally, at least 6' 3") Man would be amazing. I like feeling physically small, though I also have a bit of a bratty streak, and may even laugh at the idea of someone closer to my height being dominant, even if they have all the muscle in the world with which to overpower me. Deep down, I'm a macrophile, so not only do I like to feel small, but the idea of Men with power shrinking me a few inches is quite alluring.
There's a lot more to this particular rabbit hole, but this is a decent summary of what makes me tick.