So maybe it's just me, but it looks like there's a strap that goes over the ankle part of the boot? You could always check out frye boots, too-they have so many variations, including a boot with straps over the ankles!
If you're wanting real field boots go to the Dover Saddlery website www.doversaddlery.com. You can get a better fit and better quality boot if you go with the real thing. They also have sizing charts for the different brands to get close to a custom fit. I'd recommend the Ariats or the Grand Prix.