Sometimes called Vienna side reins - Vienna lunge reins. These Harness leather sliding side reins are used as a training aid to encourage the horse to learn to balance himself, round the back and carry himself properly on the bit. The action of the reins is similar to that of the German Martingale in that the horse adjusts himself toe the pressure of the reins without the rider pulling or a regular side rein that is stationary. Snaps are added for easy on and off.