JSFiddle - React, Tailwind, and code Playground

HTML

<ul>
  <li><a href="#">1</a></li>
  <li><a href="#">2</a></li>
  <li><a href="#">3</a></li>
</ul>

CSS

ul,li {
  display: flex;
}

li,a {
  flex-grow: 1;
}

ul {
  margin: 0;
  padding: 0;
  width: 150px;
}

li {
  border-right: 1px solid #000;
  list-style: none;
}

a {
  background: #f00;
  color: #fff;
  line-height: 50px;
  text-align: center;
  text-decoration: none;
}