Difference in x valve and rt valve

[jesseyo13]

I was wondering, other than materiel is there any difference in performnce in the retro valve and the x valve? Its hard to find any information on the difference.
Thanks

[t33kyboy]

only thing thats different is weight, material, the x valve accept ULTs and the Rt does not... and color :o (new forum smilies are ugly)