Bootstrap CSS class .mb-1 / mb-*-#

<div class="mb-0 bg-primary d-inline-block">Spaced Div</div>
<div class="mb-1 bg-primary d-inline-block">Spaced Div</div>
<div class="mb-2 bg-primary d-inline-block">Spaced Div</div>
<div class="mb-3 bg-primary d-inline-block">Spaced Div</div>
<div class="mb-4 bg-primary d-inline-block">Spaced Div</div>
<div class="mb-5 bg-primary d-inline-block">Spaced Div</div>

<!-- respsonsive viariations -->
<div class="mb-sm-5 d-inline-block bg-primary">Spaced Div</div>
<div class="mb-md-5 d-inline-block bg-primary">Spaced Div</div>
<div class="mb-lg-5 d-inline-block bg-primary">Spaced Div</div>
<div class="mb-xl-5 d-inline-block bg-primary">Spaced Div</div>