Nylon halter adjusts both around the nose and over the crown for a perfect fit. Made of 3/4 nylon to fit adult standard donkeys. Measure around the nose for nose measurement and from the nose on one side up behind the ears and back to the nose on the other side for the full crown measurement. Nose fits 15-20" and full crown 36-41". If you need smaller sizes use the miniature donkey size chart to determine sizing. https://llamaproducts.com/halter-sizing.html scroll down to see different size charts.