The FitBark GPS Fastener is a universal collar attachment for the FitBark 2 Dog GPS Tracker. You attach your FitBark to the FitBark Fastener using the standard zip ties that come with your FitBark. Then you clip the FitBark Fastener to any collar or strap up to 1.25 inches wide. Change collars as often as you want and never have to re zip tie it ever again! Our FitBark Fastener is made from an advanced plastic that is UV resistant and purposefully outdoor formulated.