The name is certainly self-explanatory. Nevertheless, here's a brief description. This LoRA helps in visualizing the underbust.

The best results are achieved with a weight of 1.7–2.0.

The trigger is "underboob." The LoRA is also trained with additional triggers: "small breast," "medium breast," "normal breast," "large breast," "huge breast," and "gigantic breast." Of course, these specific tags can also be omitted.