Not sure... I kind of feel like I don't want to buy older parts when I can put modern parts on my Ironman. When I bought the bike, the owner gave me another freewheel- a Dura-Ace MF-7400. I like the fact of having the bigger gears for those steep hills, but I don't think I'm approaching hills correctly (if I'm in the lowest gear, it's easy to lose momentum). I currently have a MF-6208 (600EX) installed.