It is an object of the present invention to provide a catalyst having excellent performance and high mechanical strength for use in the production of methacrylic acid. At least two, transversely spaced-apart loop members for receiving an elastic exercise band therethrough are attached to at least one of the plurality of horizontal strap members. The device provides a visible image of a single ring or curve when illuminated with a single light source, and three rings or curves are visible when three light sources illuminate the device.