JSFiddle - React, Tailwind, and code Playground

HTML

<div class="wrap">
  <div class="block"></div>
  <div class="block"></div>
  <div class="block"></div>
</div>

<br>
<div class="wrap">
  <div class="block"></div>
  <div class="block"></div>
  <div class="block last"></div>
</div>

CSS

.wrap {
  padding: 5px;
  border: 1px solid #000;
  display: flex;
}

.block {
  width: 50px;
  height: 50px;
  background: #000;
  
  -webkit-background-clip: padding-box;
	-moz-background-clip: padding-box;
	background-clip: padding-box;
	flex-grow: 1;
  
  margin-right: 5px;
}

.last {
  margin: 0;
}