JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="http://netdna.bootstrapcdn.com/bootstrap/3.0.0/css/bootstrap.min.css">
<script src="http://netdna.bootstrapcdn.com/bootstrap/3.0.0/js/bootstrap.min.js"></script>
<link rel="stylesheet" href="http://netdna.bootstrapcdn.com/font-awesome/3.2.1/css/font-awesome.min.css">
<i class="icon-th-list font-25em"></i>&nbsp font 2.5em<br/>
<i class="icon-th-list font-2em"></i>&nbsp font 2em <br/>
<hr>
<i class="icon-th-list"></i>&nbsp default size<br/>
<i class="icon-th-list icon-large"></i>&nbsp icon-large<br/>
<i class="icon-th-list icon-2x"></i>&nbsp icon-2x<br/>
<i class="icon-th-list font-36"></i>&nbsp font 36px<br/>

CSS

body {
}

.font-25em {
    font-size: 2.5em !important;
}

.font-2em {
    font-size: 2em !important;
}

.font-36 {
    font-size: 36px !important;
}