This bike trailer is great. As with all pets, I wasn't sure if our pitbull would like it, but since he hurt his leg and the Vet said he needs to take it easy, this is a fun way he can get some outdoor time and new smells safely.I pull him with a mountain bike, he is 52lbs and somewhat of a medium to low rider. When he sits, his head is inside and under the roofline. Although a couple times he did stand up on his hind legs and hang his front legs over the top/side. It was stable and sturdy but he wasn't going crazy inside either.. I read some reviews where some folks tipped their trailer on tight turns but we haven't had any issues and I don't take tight turns fast. The bottom is not solid/firm so to give him some stability, I found the Yellow rigid lid off those typical size home depot/lowes storage tubs was the perfect fit and rigid enough for me to put a yoga mat on top of and make him feel like the floor was stable and sturdy. No wood necessary.Let me also say it's the cutest dang thing to see a dog enjoying themselves in this! We introduced him to it while it was connected to my bike, and with treats inside and lots of praise when he got in. We let him go in and come out on his own multiple times to get treats before we zipped him in it. The top was unzipped so we fed him his favorites in the top while he got used to it too. My husband stood outside in the driveway with treats and I rode him by and stopped for more treats eaxh pass a couple times. It might sound like a lot of work but if you want your dog to like it you may need to practice a bit. The same day, we took him on a 2.5ish mile 1 way ride to a friend's house and he swam with his BFF and had a blast and was tired when we loaded him back in the trailer to ride home. He had a great time and I believe he now associates the trailer with fun or treats, and that's just what you want. Would buy again!