I just go plain for long distances, over a few hours we allow him to move free about the trailer, which is a 3 horse, and he usually goes backwards and moves around a bit. So I don't want to use polos for the risk of them coming undone! If we are going across town I do tie him up and polo wrap him, or sometimes do standing wraps. If I am just going a mile up the road I put his SMB's on and take them off when we get there since he likes to knock his legs getting in and out. No matter how long he is going to be in the trailer, I always use bell boots. Anyway, I don't believe in shipping boots, they are kinda just a waste of money, I rarely do travel so I usually just use what I already use everyday when traveling. If I did use them I would use something stiff and actually offered protection, not just a heat holder.