Not a tech, but we bought one to use for our trip and I am booster training a bit with DD now. We've used it a few times this week around town. While it is certainly convenient and will pack nicely in our luggage, it doesn't seem to have a lot of leg support. DD is on the leggy side, I think, and I keep having to remind her to keep her legs down; she wants to put her knees up and her feet on the seat and it makes the lap belt slip up on her tummy. When she sits properly I feel like it his her well though. She is 44" and 44 lb. My 6.5 yo nephew uses one full time, but I know his mom isn't big on car safety, so I don't know how it actually fits him, or how well he sits in it. I may ultimately get her something different before we go because we are planning to rent a car one day and do some driving around and I don't know if she'll be comfortable enough in it.