class used for large button in bootstrap code example
Example: large button in bootstrap
<!-- Large buttons -->
<button type="button" class="btn btn-primary btn-lg">Large button</button>
<!-- Medium Buttons -->
<button type="button" class="btn btn-primary">Large button</button>
<!-- Small Buttons -->
<button type="button" class="btn btn-primary btn-sm">Large button</button>
<!-- Block Buttons -->
<button type="button" class="btn btn-primary btn-lg btn-block">Block level button</button>