Jenson Button completed a pleasing day of practice as he topped the timesheet in this afternoon's free practice ahead of the Chinese Grand Prix in Shanghai.
The 29-year-old, who is seeking his third successive victory of the season, had finished second quickest in the morning and clocked a time of one minute 35.679 seconds in his Brawn GP car to go fastest in the afternoon.
Nico Rosberg of Williams was 0.025secs behind in second while Button's team-mate Rubens Barrichello was third fastest.
After finishing fastest in the morning session in his McLaren, world champion Lewis Hamilton clocked could only manage 13th in the second session.
The Red Bulls of Mark Webber and Sebastian Vettel impressed once again as they were fourth and fifth fastest respectively.
Their performances were all the more impressive considering they are driving cars without the double diffusers that on Wednesday were ruled legal by the FIA's International Court of Appeal.
Toyota, who have had the controversial diffuser since the start of the season, enjoyed a good session as Jarno Trulli finished sixth and Timo Glock eighth with Williams' Kazuki Nakajima sandwiched in-between.
McLaren's Heikki Kovalainen and Sebastien Bourdais of Toro Rosso completed the top 10.
It was another disappointing session for Ferrari, however, as Felipe Massa and Kimi Raikkonen finished 12th and 14th respectively.
With all the teams scrambling to make the technical adjustments to catch Brawn, Toyota and Williams, Hamilton emerged in the morning session with a new front wing and revised diffuser.
There was a clear improvement in his McLaren as the 24-year-old went fastest with a time of 1:37.334.
However, he failed to replicate that kind of performance in the afternoon as instead it was the Red Bulls who enjoyed the early dominance.
Barrichello climbed to the top just less than an hour into practice with a time of 1:35.995 before quickly improving by 0.114 and it looked as though the Brazilian would hold on to that position before Button made a late charge to clock a time of 1:35.679 and move ahead of his team-mate.