Frames can be solid or folding. Folding frames make for easy transport and storage. The folding mechanism is flexible and gives the chair a smooth ride when negotiating uneven surfaces by allowing all four wheels to stay in contact with the ground more of the time. Rigid frames are strong and light. They usually require little maintenance, which can reduce long-term costs. They have a more responsive feel and allow for more precise alignment of the wheels. This latter feature is often desirable to the young or very active user. When choosing a frame it is important to consider the vehicle that will be used to transport the chair and where the chair will be kept (i.e., in the trunk versus the back seat). How the components break down or fold for transport will be important.