When I attempted to utilize html5's form size/maxlength with bootstrap, I encountered an intriguing issue.
The .form-control class in bootstrap overrides the size, but if removed, the input loses its styling.
Check out the code pen here: http://codepen.io/rkhayat/pen/JoeBqx
Thank you!
<div class="container">
<div class="form-group">
<p>Phone</p><input class="form-control" id="inputPhone" maxlength=
"3" name="phone" required="required" size="3" title="" type="tel"
value="">
</div>
</div><!--with form-control-->
<div class="container">
<p>Note that removing form-control removes ALL styles, but retains the
size from html size input</p>
</div>
<div class="container">
<div class="form-group">
<p>Phone</p><input id="inputPhone" maxlength="3" name="phone"
required="required" size="3" title="" type="tel" value="">
</div>
</div><!--without form-control-->
Edit: After some research, I came across this http://getbootstrap.com/css/#column-sizing
Implemented bootstrap's suggested solution, although it feels like a workaround.
<div class="col-xs-4">
<div class="form-group">
<p>Phone</p>
<div class="col-xs-3">
<input type="tel" name="phone" class="form-control" value="" size="3" maxlength="3" required="required" title="">
</div>
<div class="col-xs-3">
<input type="tel" name="phone" class="form-control" value="" size="3" maxlength="3" required="required" title="">
</div>
<div class="col-xs-4">
<input type="tel" name="phone" class="form-control" value="" size="4" maxlength="4" required="required" title="">
</div>
</div>
</div>