W3Schools Tryit Editor

<!DOCTYPE html>
<html>
<head>
<style>
#main {
  width: 300px;
  height: 100px;
  border: 1px solid #c3c3c3;
  display: flex;
}

#main div {
  flex-grow: 0;
  flex-shrink: 0;
  flex-basis: 50px;
}

#main div:nth-of-type(2) {
  flex-basis: 100px;
}
</style>
</head>
<body>

<h1>The flex-basis Property</h1>

<p>Set the initial length of the flex items to 50 pixels, with an exception; set the initial length of the second flex item to 100 pixels:</p>
<div id="main">
  <div style="background-color:coral;">50px</div>
  <div style="background-color:lightblue;">100px</div>
  <div style="background-color:khaki;">50px</div>
  <div style="background-color:pink;">50px</div>
  <div style="background-color:lightgrey;">50px</div>
</div>

<p><b>Note:</b> Internet Explorer 10 and earlier versions do not support the flex-basis property.</p>

</body>

</html>