The HALTI Link is compatible for use with all HALTI Headcollars, HALTI OptiFit Headcollar, and HALTI Padded Headcollars. Easy to use and added security when using headcollars. The Halti Link is used to attach the HALTI Headcollar to your dog's collar. This reduces the possibility of more anxious or boisterous dogs being able to remove the headcollar. Put your mind at ease when walking your dog with a little extra security that the HALTI Link provides. Simple, but very effective!