Alinity's ass just looks good, there's not really any other way to put it. i don't know if its the way she presents it but its enjoyable every time. i wish she would show her pussy more though.
If I recall she and a few of her friends have had Brazilian butt lifts. Essentially they suck fat out of one area with liposuction and after it's been purified it's injected into the butt. Helps give it a more rounded and full look.