My husband and I just got back from a 7,200 mile cross country trip with our little miniature Australian Shepherd, only 14 pounds. We used the sack in Custer State Park and Yellowstone National Park when the signs said no pets on a leash. It was handy and acceptable in all areas except one in Yellowstone where a ranger said no because she could get out. I showed him how she was hooked but he said no, thankfully when he saw us we were already on our way back. We will definitely use the sack again. Very good purchase.