ui-select/src/bootstrap/choices.tpl.html

<ul class="ui-select-choices ui-select-choices-content">
  <li class="ui-select-choices-group" id="ui-select-choices-{{ $select.generatedId }}" >
    <div class="divider" ng-show="$select.isGrouped && $index > 0"></div>
    <div ng-show="$select.isGrouped" class="ui-select-choices-group-label dropdown-header" ng-bind="$group.name"></div>
    <div ng-attr-id="ui-select-choices-row-{{ $select.generatedId }}-{{$index}}" class="ui-select-choices-row"
    ng-class="{active: $select.isActive(this), disabled: $select.isDisabled(this)}" role="option">
      <span class="ui-select-choices-row-inner"></span>
    </div>
  </li>
</ul>