The Robust harness/halter has a cone-shaped device underneath which contains a freely-rotating ball, working on the same principle as a ball-pen. The stainless steel ball container can be filled with ink of the desired colour. each fill is enough to mark 25-30 cows (approx. 0.5 litre). When a cow is properly in season she will receive very clearly identifiable back marking from the bull wearing the device. marks will fade in 4 to 14 days.
