<form>

  <select class="form-select select" data-mdb-filter="true" 

          data-mdb-clear-button="true" data-mdb-visible-options="6"

          multiple onclose="this.form.submit()">

    <option selected="selected" >One</option>

    <option selected="selected">Two</option>

    <option selected="selected">Three</option>

    <option selected="selected">Four</option>

    <option selected="selected">Five</option>

  </select>

  <label class="form-label select-label">Options</label>

</form>