Most suitcases including carry-on luggage that come with wheels will come with in-line skate wheels of some kind. The distinguishing characteristics of these wheels are that they're made of a flexible polyurethane material and are recessed into the suitcase itself. Most suitcases with in-line wheels will have two or three of these wheels on one side, along with some sort of stopper that allows the bag to stand upright when not being carried.