SW-2 is the simplest type of H-to-G converter, where the converter's effect is simply to suppress a Herschel cleanly after allowing its first natural glider to escape. The name should be read as "SW minus two", where -2 is a glider lane number. The complete designation is "SW-2T21". See NW31T120 for a discussion of the standard naming conventions used for these converters.
An unlimited number of converters have the SW-2T21 classification. The variants most often used consist of just a few small still life catalysts, as shown below. The beehive one is in the infobox.