<style>
<form action="#">
<select class="form-corners">
<option value="0">Select car:</option>
<optgroup label="Car" data-max-options="2">
<option value="1">Saloon</option>
<option value="2">Coupe</option>
<option value="3">Estate</option>
<optgroup label="Van" data-max-options="2">
<option value="6">Astrovan</option>
<option value="7">Windstar</option>
<option value="8">Pacifica</option>
</select>
</form>
</style>