Choosing the right suitcase for you depends on your needs. However, buying a three-in-one suitcase set saves you the headache of selecting the correct size. A brand like Merax for example, can be purchased in a set of three, with dimensions of 20,24 and 28 inches. Each of the pieces is expandable, giving you an extra 25 percent space. They are also fitted with 360 0C spinner wheels that are ideal for smooth mobility and maneuvers.