Tailwind CSS class .flex-auto

<div class="flex bg-gray-200">
  <div class="flex-auto bg-teal-400 p-4 m-2">1</div>
  <div class="flex-auto bg-teal-400 p-4 m-2">2</div>
  <div class="flex-auto bg-teal-400 p-4 m-2">3</div>
</div>

.flex-auto {
    flex: 1 1 auto;
}