v>

<div class="grid--content-box">
<div class="grid__col-4">
    4
</div>
<div class="grid__col-8">
    8
</div>
</div>

<div class="grid--content-box">
<div class="grid__col-5">
    5
</div>
<div class="grid__col-7">
    7
</div>
</div>

<div class="grid--content-box">
<div class="grid__col-6">
    6
</div>
<div class="grid__col-6">
    6
</div>
</div>

<h3>$flexbox-grid-mixins-box-sizing: null; (Not output box-sizing property. Usually the initial box size value as content-box)</h3>

<div class="grid--nul