Example
Markup
<label class="specialradiobox" for="specialradioboxradio1">
<input type='radio' name='specialradiobox' id='specialradioboxradio1' value='' checked='checked'>Radio 1<i for="specialradioboxradio1"></i>
</label>
<label class="specialradiobox" for="specialradioboxradio2">
<input type='radio' name='specialradiobox' id='specialradioboxradio2' value=''>Radio 2<i for="specialradioboxradio2"></i>
</label>
Source:
build/doc/doc.css, line 3856