These are seriously the toughest bell boots I've ever used. They stay on in the muddiest turnout situations, rinse right off and dry quickly. These were the only bell boots my Houdini never figured out how to remove and he wore them 24/7. Large size is out of stock on the ThinLine webiste right now, but I happen to have this brand new pair and no horse to use them on. The patented latch design offers durability and protection for your horse and peace of mind for you during turnout. Redesigned from the ground up, this one-piece polymer horse bell boot offers unmatched durability and protection for your horse. GatorBootz has a patented latch designed to be opened by humans but not equines. By eliminating typical Velcro closures, the lifespan of bellboots is extended, and the hassles are reduced. Sizing and Fit Gatorbootz bell boots make contact with the hoof, not the soft tissue, making sizing simple. It’s determined by hoof size so if you know your horse’s shoe size, you’ll know just what size Gatorbootz to order. More info available on the ThinLine website: https://thinlineglobal.com/horse-tack-equipment/gatorbootz-bell-boot-fail-proof-closure