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Bootstrap class: .dropdown-item-text

<div class="dropdown open">
  <button class="btn btn-secondary dropdown-toggle"
          type="button" id="dropdownMenu4" data-toggle="dropdown"
          aria-haspopup="true" aria-expanded="false">
    Dropdown
  </button>
  <div class="dropdown-menu">
    <span class="dropdown-item-text">Dropdown item text</span>
    <a class="dropdown-item" href="#">Action</a>
    <a class="dropdown-item" href="#">Another action</a>
  </div>
</div>

Preview

Sass source

/* _dropdown.scss:162 */
.dropdown-item-text {
  display: block;
  padding: $dropdown-item-padding-y $dropdown-item-padding-x;
  color: $dropdown-link-color;
}

Uses variables

/* _dropdown.scss:162 */
$dropdown-item-padding-y
$dropdown-item-padding-x
$dropdown-link-color