Williams is testing a radical rear wing design during the opening day of the post-race at the Circuit de Barcelona-Catalunya.
Alex Lynn took to the circuit with a rear wing which featured additional wings above the standard design. The front wing also features some additional components, with Williams telling F1i the designs are "to gain a better understanding of the car aero balance over a lap" and relevant to both this year and 2017.
The design is not legal under the current regulations but teams do not have to pass FIA scrutineering during testing and can therefore run whatever they choose.
Williams has yet to score a podium this season, and is currently fourth in the constructors' championship behind Mercedes, Ferrari and Red Bull.
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