I purchased this in a LARGE for our 5 month old pup who is currently 16 lbs and will be 27-33lbs most likely. Her neck to tail length is 20” currently. I purchased this to not only keep her safe, but to help lift her up to see out the window as her car anxiety and motion sickness was really complicating life and making for brutal clean up several times a week. I purchased a “like new/open box” seat. I am a fan of this seat for sure. I will explain more about the seat and how we have worked to ease our pup’s anxiety, but will first explain our “open box” experience…The seat was of beautiful construction out of the box, but our dog would fall out of the seat (note last picture) and vomit in the car all over the seat and on the car’s seats since the seat didn’t contain her. After washing the seat and cleaning the car twice (what a project!), I then went back to the product info and realized our seat did not include the foam wall inside the seat. I should have realized this sooner, but trusted that we had a complete product as “like new/ open box” had always been a good experience for us prior. So I called customer service and Amazon refunded the entire seat as the seat company nor Amazon could offer a replacement foam wall. I then purchased a 3” thickness roll of foam and eyeballed the dimensions as best I could because I didn’t want to waste the seat. The seat was saved.Now, my thoughts on the seat: It’s high quality, easily washable though putting the foam pieces back inside the washed outer seat takes some time. It has definitely helped elevate our pup and lift her head towards the window so she can get fresh air and look out which has definitely aided her to stopping vomiting in the car.To ease her into a positive experience in the seat, I allowed her to nap in it in our living room. She enjoyed the comfort. Then I installed it back in the car. My husband and I have worked towards easing her car anxiety by exposing her everyday to short car rides. We have worked up to faster speeds and longer distance. She is still anxious (some days more than others), but she has not vomited since in the car.I’m very grateful for this seat and highly recommend it for dog owners. While our experience wasn’t straight forward, the product is worth an investment for the safety and comfort of your dog, especially if car sickness is an issue.