JSFiddle - React, Tailwind, and code Playground

HTML

<div class="post">
  <div class="container">
    not single post
  </div>
</div>

<div class="single-post">
	<div class="container">
    single post
  </div>
</div>

CSS

.container {
  background-color: lightblue;
  margin: 1em 0;
  padding: 1em;
  width: 92%;
}

.single-post .container {
  width: 60% !important;
}