We sent in pictures and girth size of our 10 month old, and were recommended harness sizes to order which was very helpful. We received harness but thought it wasn't quite right for size. After sending pictures in wearing harness we were advised it did indeed look a bit snug towards front legs, and were sent out two different part sizes to mix and match. The harness itself is very well designed due to it coming in 3 parts, if one part wears out or becomes too small, only one part needs replacing, not the whole harness. Cannot fault service and advice we received, and will definitely recommend to other doggie parents.