Originally Posted by ThermionicScott

The HG cassettes always used three rivets or bolts to hold the stack of cogs and spacers together -- the nicer ones used the bolt that you could unscrew to customize cassettes. It's only recently that they've started making cheaper cassettes (HG20, non-Japan) where the larger cogs use the next larger one as a carrier, and they can't be completely taken apart. Just FWIW...