I bought this coat for my border collie. Based on the size guide, he was closest to a medium. But, when I received it, the jacket was slightly short in the back and had a HUGE belly band - by several inches beyond the velcro closure. Even if I made adjustments myself, the rear sides of the jacket stick out awkwardly, making it an overall poor fit for my dog, especially considering the cost. Since I'm afraid that sizing up will just make it huge all-around, this is going back for a refund. Disappointed as I was so looking forward to having this for when we run Fast CAT.