Ansterdam is an R class ship -- midsize.
S class ships: Statendam, Maasdam, Ryndam and Volendam -- smallest original HAL ships.
R class ships: Rotterdam, Amsterdam, Zaandam and Volendam.
Vista class ships: Zuiderdam, Oosterdam, Westerdam and Noordam
Signature class ships: Eurodam and Nieuw Amsterdam
The Prinsendam is in a class of herself as she is the smallest ship -- but originally built for HAL -- she came from the Royal Viking line.
Soon to come in the fall of 2015 -- a Pinnacle class ship -- 99,000 tons.