There is an option available to customize the classname for the sbHolder object, but reluctance to change it due to the necessity of rewriting the CSS. It would be beneficial if an additional class could be set for application, yet this feature is lacking.
A workaround involves enclosing the select element within a wrapper and utilizing CSS to override the default width http://jsfiddle.net/FQKax/8/
.wrapper-one .sbHolder{
width: 500px;
}
.wrapper-two .sbHolder {
width: 200px;
}
<div class="wrapper-one">
<select id="language">
<option value="javascript">Javascript</option>
<option value="objective-c">Objective C</option>
<option value="python">Python</option>
</select>
</div>
<br/><br/>
<div class="wrapper-two">
<select id="language2">
<option value="javascript">Javascript</option>
<option value="objective-c">Objective C</option>
<option value="python">Python</option>
</select>
</div>
Extra markup is necessary for this solution, unlike @cih's method which relies on jQuery to individually mark each instance accordingly http://jsfiddle.net/FQKax/37/
$("#language").selectbox();
$("#language2").selectbox();
$(".sbHolder").each(function(index){
$(this).addClass('instance-' + index);
});
.instance-0.sbHolder{
width: 500px;
}
.instance-1.sbHolder {
width: 200px;
}