flex-shrink

flex-shrink: 2;
flex-shrink: 0.6;

/* Global values */
flex-shrink: inherit;
flex-shrink: initial;
flex-shrink: unset;

<number>

<p>The width of content is 500px; the flex-basis of the flex items is 120px.</p>
<p>A, B, C have flex-shrink:1 set. D and E have flex-shrink:2 set</p>
<p>The width of D and E is less than the others.</p>
<div id="content">
  <div class="box" style="background-color:red;">A</div>
  <div class="box" style="background-color:lightblue;">B</div>
  <div class="box" style="background-color:yellow;">C</div>
  <div class="box1" style="background-color:brown;">D</div>
  <div class="box1" style="background-color:lightgreen;">E</div>
</div>

#content {
  display: flex;
  width: 500px;
}

#content div {
  flex-basis: 120px;
? border: 3px solid rgba(0,0,0,.2);
}

.box { 
  flex-shrink: 1;
}

.box1 { 
  flex-shrink: 2; 
}