i don't know you can find out on their website but at Fort William we took a dander round the opits and had an oggle at affy's bike...it only had 4 sprockets at the rear and the mech was limited off. I'm guessing this was to save weight but it looked pretty rad.
Last time I rode with dan and gee. I talked to Dan about his cassette (his is like some funky half cassette) and he said that is saves weight and is really all you need.