The following code shows how to create input-group-addon.
<!DOCTYPE html>
<html>
<head>
<link rel="stylesheet" type="text/css"
href="http://netdna.bootstrapcdn.com/bootstrap/3.0.0/css/bootstrap.min.css">
<style type='text/css'>
.svX3 {<!-- w w w.j a v a 2s. co m-->
width: 100%;
}
</style>
</head>
<body style='margin:30px'>
<form>
<div class="form-group input-group">
<span class="input-group-addon">X</span>
<input type="text" class="form-control">
<span style="width: 55px;" class="input-group-addon">km</span>
</div>
<div class="form-group input-group">
<span style="width: 55px;" class="input-group-addon">X</span>
<input type="text" class="form-control">
<span class="input-group-addon">km</span>
</div>
<div class="form-group input-group svX3">
<span style="width: 55px;" class="input-group-addon">X</span>
<input type="text" class="form-control">
<span style="width: 55px;" class="input-group-addon">km</span>
</div>
</form>
</body>
</html>