I recently bought two of these booster seats; one for each of my twins. They of course were very excited to get out of their full booster seat into these cool, smaller booster seats. These seats are meant for 4 year olds to 10 year olds that are 40 pounds to 100 pounds, and 40 inches to 57 inches in height. I have a 3 1/2 year old as well that is still in a full Graco booster, so it is very hard to get three car seats in the back of my SUV, in the back of any vehicle I am sure. I researched and found that this backless booster is one of the narrowest, so that is one of the reasons I went with this one, in hopes that all three seat would fit well in the back of my SUV. So far so good. It is a tight fit, but they all do fit. This backless booster does have cup holders on either side as well, but with the three car seats in the back, we don't get to use these, but they would be a great thing to use if we didn't have the tight fit. It goes in/out of the car very easy (lightweight), and the cover also comes off for easy cleaning. I really like this seat and recommend it!