Please pay careful attention when purchasing a used car seat. Here are some tips to consider: does the car seat have a National Safety Mark, like the one pictured here for Canada. Is there an instruction booklet? Is the car seat appropriate for the development, weight and height of your child? If the car seat has an expiry date, will the time period cover your needs? Can the car seat be installed correctly in your vehicle? Are the harness and tether straps easy to adjust? Are all of the pieces present with the seat? Has it been the subject of any recalls? Ask the seller if its been in any collisions, however minor, or dropped from a height of three or more feet? Has the seller made any alterations, changed the routing of the straps or added any extra pieces? More info can be found at the Transport Canada website and in the U.S. see the section "How to Keep Your Child Passengers Safe on the Road" at the bottom of the National Highway Traffic Safety Administration home page.