I think the 68/73mm tube has a slip joint in it. The fsa ones definitely do.
It'll squish it if you try to fit it in a 68mm shell without the spacers, but there's a little bit of leeway as it's not supporting anything just keeping it clean, they're not like the FSA ones though.
@snottyotter started
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I think the 68/73mm tube has a slip joint in it. The fsa ones definitely do.