<div class="btn-group">
    <button class="btn btn-default">1</button>
    <button class="btn btn-default">2</button>

    <div class="btn-group">
      <button type="button" class="btn btn-default dropdown-toggle" data-toggle="dropdown">
        Dropdown <i class="fa fa-caret-down"></i>
      </button>
      <ul class="dropdown-menu">
        <li><a href="#">Dropdown Link</a></li>
        <li><a href="#">Dropdown Link</a></li>
      </ul>
    </div>
  </div>