I have Woof Brushing boots....front and hind. While I do like them, my experience has been that they run large.
My gelding typically wears a large front boot, and extra large hind boots (SMB, etc.). He is 16.0 hands and is a Percheron/TB cross....so while he is not overly tall, he does have more substantial bone.
In the Woof boots, however, he wears a medium in the front a large in the back. I tried his normal sizing (large front, xl hind) and he swam in them.
Perhaps this is just my odd experience, but I wanted to pass it along.
"The best and most beautiful things in the world cannot be seen or even touched....they must be felt with the heart." - Helen Keller