Bootstrap CSS class .flex-*-shrink-1

<div class="d-flex text-white">
  <div class="p-2 w-100 bg-primary">Flex item</div>
  <div class="p-2 flex-shrink-1 bg-success">Flex item</div>
</div>

<div class="d-flex text-white mt-2">
  <div class="p-2 w-100 bg-warning">Flex item</div>
  <div class="p-2 flex-sm-shrink-1 bg-danger">Flex item</div>
  <div class="p-2 flex-md-shrink-1 bg-warning">Flex item</div>
  <div class="p-2 flex-lg-shrink-1 bg-danger">Flex item</div>
  <div class="p-2 flex-xl-shrink-1 bg-warning">Flex item</div>
</div>