Bootstrap 3.0 - Grid System

HTML

<link rel="stylesheet" href="//netdna.bootstrapcdn.com/bootstrap/3.0.0/css/bootstrap.min.css">
<script src="//netdna.bootstrapcdn.com/bootstrap/3.0.0/js/bootstrap.min.js"></script>
<div class="container">

<div class='row flex'>
    <div class="col-xs-2 stretch"><div class="well">QWE</div></div>
    <div class="col-xs-6 stretch"><div class="well">ASD</div></div>
    <div class="col-xs-4 stretch"><div class="well">
      Lorem ipsum dolor sit amet, consectetur adipisicing elit. Delectus recusandae quis autem nam maxime non magni facere? Officiis, nesciunt. Magnam beatae praesentium nam reprehenderit, cumque fugiat nemo fugit voluptatem omnis.
    </div></div>
</div>
<div class='row'>
    <div class="col-xs-4"><div class="well">RTZ</div></div>
    <div class="col-xs-5"><div class="well">FGH</div></div>
    <div class="col-xs-3"><div class="well">VBN</div></div>
</div>
</div>

CSS

.flex {
  display: flex;
}

.stretch {  
  align-items: stretch;
}

.stretch > .well {
  height: 100%;
}