We tried many harness for our 10 lb. Yorkie mix puppy. This one was by far the best. It's easier to put on a rambunctious puppy compared to the others. It's very secure with both the Velcro closure and double D ring latch. The small size was slightly large for our pup when she was 8 lb but it was usable. I would say that it would still be good when she is 12 lb.