Hoover is also notable for an extremely unusual vacuum cleaner, the Hoover Constellation, which is canister type but lacks wheels. Instead, the vacuum cleaner floats on its exhaust, operating as a hovercraft. Introduced in 1952, they are quite collectable today, and are easily identified by the spherical shape of the cannister. They tended to be loud, had relatively poor cleaning power, and could not float over carpets. But they remain a very interesting machine; restored, they work well in homes with lots of hardwood floors.