<div class="btn-group btn-group-lg" role="group" aria-label="Basic example">
    <button type="button" class="btn btn-secondary">Left</button>
    <button type="button" class="btn btn-secondary">Middle</button>
    <button type="button" class="btn btn-secondary">Right</button>
</div>

<div class="btn-group" role="group" aria-label="Basic example">
    <button type="button" class="btn btn-secondary">Left</button>
    <button type="button" class="btn btn-secondary">Middle</button>
    <button type="button" class="btn btn-secondary">Right</button>
</div>

<div class="btn-group btn-group-sm" role="group" aria-label="Basic example">
    <button type="button" class="btn btn-secondary">Left</button>
    <button type="button" class="btn btn-secondary">Middle</button>
    <button type="button" class="btn btn-secondary">Right</button>
</div>