both the inner and outer thickness and the length makes the smooth lips look so nice. The outer lips are detailed with full skin texture, its nice the see the detail they sculpted in. It’s holding up well so far also. I usually tear the outer hole in the first couple of sessions and eventually tear the inner lining also. No tears at all on this one. Now it’s the feel and sensations of this that I don’t really care for. It’ll get the job done. It’s just not that great. And the worst part of all is that it’s noisy. A lot of gurgling while you’re stroking it. I don’t care for all that noise at all. You spend the hole time trying to keep it from making the gurgling sounds. It feels very artificial too. The way the tunnel zig zags around just doesn’t cut it for me. I have the Zhang Xiao Yu, so I compared them side by side and the Zhang Xiao Yu feels so much better.