Hardly used. Size S (Comfortable for a weight of 5.4kg / back length of 40cm) For dogs with a shorter back length, it can be used unfolded. Up to 5kg: Plenty of room to use comfortably. 6-8kg: Fits the body when sleeping curled up, but the front paws may stick out when sleeping with the back stretched out. 9-10kg: Quite tight, but can sleep curled up. (※Individual differences depend on back length and leg length.)