An extrudate catalyst suitable for auto emission control is made from a solid, transitional alumina. It has a partially hollow interior and one or more platinum group metals deposited on the extrudate. The cylindrical extrudate has internal reinforcing vanes or ribs extending from the inner wall to the center of the extrudate particle. This configuration permits the catalyst to have the large geometric surface area per reactor volume yet, because of the openings inside the extrudate, the catalyst particles do not exhibit a large pressure drop when packed in a deep bed. These catalysts provide greater hydrocarbon and carbon monoxide conversions than do similar size spherical particles and they have improved light-off characteristics.