This is a very thoughtful and well designed product. The inventor found traditional car seats unwieldy. In addition the author as many of us can testify found there were times were he needed a car seat and did not have one with him.
This seat truly is small enough to go in a backpack. For me the convenience is to put it in the seat back pocket of my car. There are times when I have been asked to pick up a grandchild due to my kids having a scheduling conflict. This often entails a drive home or a drive to their home to get a car seat. This unit allows you to avoid that inconvenience.
The seat installs easily. You just drop it on the seat and then run the lap belt through the attached wings on the booster seat. I found the shoulder harness fastener a bit more trouble. I advise that you shorten that strap prior to putting a squirmy kid on the booster. The clip/holder was surprisingly difficult to adjust. It seems like it should adjust more easily but it didn't.
If you have had two or more grandchildren in your back seat, all using boosters or car seats, you know there is a major problem with space. I have a mid-size SUV that seats 3 adults in the back easily but three car seats are problematic. This booster would allow three booster to easily fit into most seats. That is a major benefit.
This should be a no brainer for grandparents who are often asked for kid pickup with little or no notice. Keeping one or more of these in the car will not impact normal use of the car space. Parents will find this convenient as well, particular when there may be more than on car seat in use.
This was the part that was hard to adjust.
My only complaint was the difficulty adjusting the shoulder strap holder.