The only original, some refer to this product as a miracle, (its a wunderbar!) the bar slides behind the last cow in the row and locks on infinately. Much better than chains or other contraptions, Also great for a vet race! Now all new variable lock on shoes makes this system even easier to use because in this innovative new design it fits rails 42mm OD to 60 mm OD. Many thousands off these in use, if you have an old unit and need a new head, we have retrofit units which will very likely fit your unit