Williams surprised the paddock on the opening morning of the Barcelona in-season test by running a radical double-decker rear-wing and large struts on its front-wing.
Alex Lynn did an initial run with the devices fitted, with the rear-wing in particular causing a stir. It features a double-decker design which extends forward of the wing, as well sideways with two small winglets.
The wing isn't however being tested for an eventual debut, as it extends outside the regulated dimensions and is therefore illegal.
It's likely Williams are trying to simulate greater downforce, similar to 2017 levels, to understand tyre and aerodynamic loads, or alternatively to simulate higher-downforce requirements to improve its chassis and balance.
