In Bootstrap 3 they do not have separate classes for different styles of labels.
http://getbootstrap.com/components/
However, you can customize bootstrap classes that way. In your css file
.lb-sm {
font-size: 12px;
}
.lb-md {
font-size: 16px;
}
.lb-lg {
font-size: 20px;
}
Alternatively, you can use header tags to change the sizes. For example, here is a medium sized label and a small-sized label
<link href="http://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css" rel="stylesheet"/>_x000D_
<h3>Example heading <span class="label label-default">New</span></h3>_x000D_
<h6>Example heading <span class="label label-default">New</span></h6>
_x000D_
They might add size classes for labels in future Bootstrap versions.