Hot to get ID of record inserted using model "save()" method

Hi guys,
I need to get (automatically generated) ID of record inserted in db using model "save()" method.

PHP Code:

$product = new Product();

if ($product->save($this->request->getPost()))
{
    echo $ID; // <-- how do I get it?
} 


I know the model contains a shared instance of Query Builder but I can't access "db->insertID()" because "db" is a protected property.
Any help?
Thanks.