JSFiddle - React, Tailwind, and code Playground
HTML
<div class="container">
<div class="input-group">
<input id="ban_time" type="number" class="form-control" value="10" style="width: auto">
<select class="form-control" style="width: auto">
<option selected="">seconds</option>
<option>minutes</option>
<option>hours</option>
<option>days</option>
<option>weeks</option>
</select>
</div>
</div>
CSS
@import url("https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css")