A roll bar does two unrelated things: protect in the event of a rollover and stiffen the body. On a convertible, which has lost its roof and a significant amount of rigidity, the difference can be felt from the first bump - less shaking in the windscreen, with the front axle staying aligned with the rear.

These are style and stiffening roll bars, designed for road use and unrestricted track days. Timed competition under a racing license requires a roll bar approved by the relevant federation, along with its documentation: this is not the same part.