For more icon details, please visit Material Icon official website.
<a class='btn primary lg'><span class='icons'>face</span>large</a>
<a class='btn secondary lg'><span class='icons'>face</span>large</a>
<a class='btn primary md'><span class='icons'>face</span>medium</a>
<a class='btn secondary md'><span class='icons'>face</span>medium</a>
<a class='btn primary sm'><span class='icons'>face</span>small</a>
<a class='btn secondary sm'><span class='icons'>face</span>small</a>
<a class='btn primary xs'><span class='icons'>face</span>extra small</a>
<a class='btn secondary xs'><span class='icons'>face</span>extra small</a>