Bought this item to replace an older model which had recently died after about 5 years. This new one works great and synced perfectly with the existing collars. My only complaint is that this one does not have a "Break Alarm" to let you know if the loop is not functioning. So the only way to know is to actually look at the indicator lights. The alarm was a nice feature because the unit is not in a convenient location to glance at it, but this is a minor inconvenience. Just need to make a point to periodically check.