Bootstrap class: .justify-content-center

    <div class="d-flex flex-wrap justify-content-center bg-secondary" style="height: 50px;">
        <div class="px-4 bg-primary"></div>
        <div class="px-4 bg-info"></div>
        <div class="px-4 bg-primary"></div>
        <div class="px-4 bg-info"></div>
        <div class="px-4 bg-primary"></div>
        <div class="px-4 bg-info"></div>
    </div>

Preview

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