A hubcap, wheel cover or wheel trim is a decorative disk on an automobile wheel that covers at least a central portion of the wheel. Cars with stamped steel wheels often use a full wheel cover that conceals the entire wheel. Cars with alloy wheels or styled steel wheels generally use smaller hubcaps, sometimes called center caps. Alternatively, wheel cover refers to an accessory covering an external rear-mounted spare tire (also known as a spare tire cover) found on some off-road or survival-type vehicles.The first hubcaps were more commonly known as dust or grease caps. These caps threaded onto the center hub on the wood, steel, or wire wheel. These were made from the beginning to 1932. Pre-1915 were all mostly made of brass that was nickel plated. The 1920s were all mostly aluminum. Grease caps of the wire wheel brands such as Houk, Hayes, Frayer, Dayton, Buffalo, House, Phelps, Pasco, Rudge Whitworth, Budd, and Stewart are some of the hardest to find.