In the 8th edition Tyranid codex, on page 91 for Ripper Swarms, the unit description text is as follows:
This unit contains 3 ripper swarms. It can include up to 3 additonal Ripper Swarms (Power Rating +2) or up to 6 additional Ripper Swarms (Power Rating +3). Each model is armed with claws and teeth.
This doesn't help that you can't buy Ripper Swarms on their own. So far, I've collected models that seem to be given as a bonus for buying other unit boxes. I've found that if I purchase a Termagaunt or Hormagaunt unit box, they'll come with three models of Ripper Swarms, but if I buy a Genestealers unit box, it will come with two models of Ripper Swarms.
How many models actually make up a Ripper Swarm? The unit description states a wounds of 3. Does that mean that each model has 3 wounds, and a full unit is nine models, for a total of 27 wounds?
Or are you supposed to collect a handful of these, and glue two or three onto a single base and then that base has 3 wounds? Which then a full unit is three bases, for a total of 9 wounds?