<!-- large size -->
<input class="form-control form-control-lg" type="text" />
<select class="form-select form-select-lg">...</select>

<!-- default -->
<input class="form-control" type="text" />
<select class="form-select">...</select>

<!-- small size -->
<input class="form-control form-control-sm" type="text" />
<select class="form-select form-select-sm">...</select>