I used a piece of cardboard to trace the hoof to get the perfect fit. I recommend doing the same. Easy to put on. Stayed in place long enough for the ugly rockfall to heal. This horse was lame on three legs and had a sound boot. Carried her in the stable with no problems and then in a small paddock for a week. Next time I use it I'll have to get a new insole as the original has been shredded but other than that it's still in great condition!