@adobe/spectrum-css/dist/components/well/index-lg.css

The Spectrum CSS top-level backwards compatible package

.spectrum-Well {
  display: block;
  min-width: 248px;
  padding: 16px;
  margin-top: 4px;
  border-width: 1px;
  border-style: solid;
  border-radius: 5px;
}