You get the absolute bare minimum required by your state, it basically just covers the other driver you hit. It's pretty awful since if you are badly injured beyond what their underinsured driver's coverage is for, you're likely not going to get a lot of money. You'll definitely get everything their policy states but the remainder comes out of your own uninsured motorist coverage and health insurance. People that buy bare minimum coverage typically don't have a lot of assets so there'll be nothing to recover from them directly.