Have a Chihuahua of 2,5kg and 1,8kg of a Chihuahua Pinscher. I was looking for a bag that you can wear well on the side without having to "clunky" acts. Nevertheless, each dog should find place. The Small fit in great. The floor does not bend through. Even the "big" does not have problems. He can not lie down and make long, but he can sit relaxed and see out front. Super is that the recess is not forward too high. This means that the two can stick out, without having to make a long neck :) For both dogs the bag is of course too small, but also have only one for a searched. For events where the dog usually goes down in dimensions, can not be topped. I have many bags compared and I found most of them with a length of 45-50cm just too big / too long. This could already not again bear reasonable under the arm you. This, however, is super and perfectly adequate :) Shoulder strap can be adjusted both :)
