I think there are only two models - one is very basic (the one we have - has a volume control and that's about it) and the other has a few more bells and whistles. We've found it to be very good, the noise reduction on the helmets is very good and providing you've got the helmets plugged in to the right input we've not had any trouble hearing each other (the co-drivers input provides a louder output - so you can talk over your driver
).