<div class="modal">
<div class="modal-dialog modal-sm" role="dialog" aria-hidden="true">
<div class="modal-content">
...
</div>
</div>
</div>
<div class="modal-backdrop" aria-hidden="true"></div>
<div class="modal">
<div class="modal-dialog modal-lg" role="dialog" aria-hidden="true">
<div class="modal-content">
...
</div>
</div>
</div>
<div class="modal-backdrop" aria-hidden="true"></div>