[labatt]

New bearings (Torlon) so smoother operation, better halyard swivel, dual tracks, removable drum (if you care about racing). Oh yeah - and it comes with a crappy furler line (very slippery) so expect to replace it. We went from a Mark I to the Mark IV. It's definitely a lot easier to manage under load, but that could have been due to the upkeep of our prior furler (which was replaced due to the torque tube splitting). In general, we like it. By the way, it uses new foils so you will have to replace your current ones, meaning you will also probably have to replace your headstay.