These spirals can be ordered from Oesco or AMLeonard- in different heights. Not only are they futile when dealing with pine voles but also they can provide a false sense of security that is shattered when the snow gets high! I use them in addition to my trapping and sometimes have damage from borers, probably as a result of not removing them in summer. They do need to be monitored for excessive tightness and they will sometimes girdle trees.