Mercedes has continued its aggressive development push at this week's Magny-Cours Formula 1 test, with Sam Bird adding valuable mileage to the team's new double-DRS.
Following baseline tests with a new Coanda-effect exhausts at the start of the young driver test on Tuesday morning, Mercedes later on added additional elements for the double-DRS to feed air to its rear wing.
It was the second time Mercedes has tested its double-DRS components, following an initial evaluation of parts for it in Friday practice for the Belgian Grand Prix.
The new-style double-DRS, similar to that which was run for the first time by Lotus in practice for the German GP, helps stall the rear wing for a straightline speed boost.
The device will be particularly valuable at tracks with medium-speed corners and long straights - such as Suzuka.
Mercedes team principal Ross Brawn told AUTOSPORT earlier this week that testing of the system would be extensive.
"There is still a long way to go," he said. "There are some races later in the year where that philosophy might be quite useful.
"It's a passive system - and can only work in certain combinations of corners. With the Ascari chicane at Monza, the corner was a bit quick to be able to use the system.
"It's about how you use it on track and it's not suitable for all tracks. It has to be tuned and the tuning is a challenge."
Bird was third quickest on the opening day of the test, after completing 95 laps, and was happy with how its first day back in F1 machinery had gone.
"We've had a very productive first day of the test today and were able to complete everything that we had planned on our programme," he said.