A wheel center cap is a decorative piece that covers the center of an automobile wheel and helps keep dirt away from the wheel bearings and the axle. Depending on the model, a wheel cap covers the lug nuts if the lug nuts are not part of the design.
In models that hide the lug nuts, they are held on using spring clips or tiny screws. In the alternative design, the wheel center cap fits over the lug posts and the lug nuts are fastened into place. The manufacturer's logo is often found in the center of the cap.
Wheel center caps are an alternative to the full hubcaps found mostly in older cars, that cover up the entire wheel and were usually pounded or clipped into place. While hubcaps had a tendency to fall off if the car hit a large bump in the road, wheel center caps usually stay on. The falling off problem is eliminated entirely with the use of the wheel caps that screw on with the lug nuts.
One type of decorative wheel center cap, the spinner, became popular in the 1960s. These originally came with protruding pieces that would spin whenever the wheel rotated. Though the protruding pieces were made illegal, modified spinner wheel caps still have a following, especially among hip-hop fans.