Standard Nathe 7.5cm Ring Ideal for sensitve mouthed horses. £46.95 imperial size: [Choose]5.5"5" Quantity: at £46.95 each Add To Basket A very soft, bendy mouthpiece. Ideal for horses that won't take the contact or for sensitive mouthed horses. 7.5cm diameter ring. New sizes for the standard Nathe are 13cm and 14cm. In other words just over 5" and 51/2".