Alex

element:nth-last-child(1), 
element:nth-last-child(2) { }

* {
    outline: 1px solid tomato !important;
}

<div class="main">
  <div style="display: inline-block; margin: auto;">
    <div class="wrapper">
      <div>
        1
      </div>
      <div>
        2
      </div>
      <div>
        3
      </div>
      <div>
        4
      </div>
      <div>
        5
      </div>
      <div>
        6
      </div>
    </div>
  </div>
</div>