Parallel kit
A parallel kit is a cable set that links two inverter generators so their outputs combine into one circuit — two 2,200 W units become roughly 4,000 W of capacity. Only inverter generators designed for paralleling (usually matched models) support it.
Paralleling works on inverter generators because their electronics synchronize the synthesized waveforms; conventional generators cannot safely do this. Most kits also provide a higher-amperage outlet (often 30 A) that neither unit has alone.
The appeal is staged buying and redundancy: one light, quiet unit covers camping, and a second identical unit joins it for outages — if one fails, you still have half your capacity, which a single large generator cannot offer.