<select ng-model="limit">
<option value="5" ng-selected="true">5</option>
<option value="10">10</option>
<option value="15">15</option>
</select>
$scope.limit = 5
<select ng-model="limit" class="ng-pristine ng-valid ng-touched">
<option value="? number:5 ?"></option>
<option value="5" ng-selected="true" selected="selected">5</option>
<option value="10">10</option>
<option value="15">15</option>
</select>