JSFiddle - React, Tailwind, and code Playground

HTML

<div class="line"></div>

CSS

.line {
  position:relative;
  width:200px;
  height:6px;
  background:red;
  margin:100px;
}

.line:after {
  position:absolute;
  content:'';
  width:0;
  height:0;
  border:3px solid transparent;
  border-left:70px solid red;
  top:0;
  right:-70px;
}