Formfit Short Walker Boot

Q: I wish to buy an Ossur Formfit short medical fracture boot from you but am unsure of the size, I am a size 10 or 11 shoe depending on the shoe and it is for my left foot which has a 4th metatarsal fracture. Please could you email me the size I should purchase. I am at present wearing a full size boot size medium but this was my wife's. It appears to fit OK and my toes are not beyond the end of the sole. Your advice please. Thanks Ian