This is the VXs which is a mid cage Vx model with the quick cage... a feature that I love and wish modern derailleurs had. the chain can be removed from the derailleur without breaking it and makes wheel removal very nice.
I run one of these on my folding touring bike... the mid cage can handle a 30 tooth cog and has a total capacity of 28 teeth and it has been performing flawlessly for many thousands and thousands of miles.
Seriously...I consider these to be among the best derailleurs ever made and the VXs only weighs 211 grams which puts it very close to being race weight.
http://www.disraeligears.co.uk/Site/...282500%29.html