Get a size smaller!
I have to small dogs, one with ~42cm back length and the other 33cm back length. I opted for a size 40 and a size 35... Turns out these coats are cut larger though! Both my dogs got lost in their intentional sizes. Fortunately, the size 35 fits my "larger" dog. I will need to order a size 30 for my smaller dog! Other than that I think this is a great product!