H jmontano,
You can add data-size in the html.
Or override CSS property.
<style type="text/css">
div.dropdown-menu.open
{
max-height: 10px !important;
overflow: hidden;
}
ul.dropdown-menu.inner
{
max-height: 10px !important;
overflow-y: auto;
}
</style>
HTML
Using data-size
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title></title>
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" />
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/bootstrap-select/1.12.2/css/bootstrap-select.min.css" />
<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
<script type="text/javascript" src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
<script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/bootstrap-select/1.12.2/js/bootstrap-select.min.js"></script>
</head>
<body>
<select name="ddlFruits" id="ddlFruits" class="form-control selectpicker" data-show-subtext="true"
data-live-search="true" data-size="3" style="width: 100px;">
<option value="Mango">Mango</option>
<option value="Apple">Apple</option>
<option value="Banana">Banana</option>
<option value="Orange">Orange</option>
</select>
</body>
</html>
Demo
Using CSS
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title></title>
<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css" />
<link rel="stylesheet" href="https://cdnjs.cloudflare.com/ajax/libs/bootstrap-select/1.12.2/css/bootstrap-select.min.css" />
<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js"></script>
<script type="text/javascript" src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"></script>
<script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/bootstrap-select/1.12.2/js/bootstrap-select.min.js"></script>
<style type="text/css">
div.dropdown-menu.open
{
max-height: 10px !important;
overflow: hidden;
}
ul.dropdown-menu.inner
{
max-height: 10px !important;
overflow-y: auto;
}
</style>
</head>
<body>
<select name="ddlFruits" id="ddlFruits" class="form-control selectpicker" data-show-subtext="true"
data-live-search="true" style="width: 100px;">
<option value="Mango">Mango</option>
<option value="Apple">Apple</option>
<option value="Banana">Banana</option>
<option value="Orange">Orange</option>
</select>
</body>
</html>
Demo
