Table:
text: Bob Bryan career statistics
Doubles: 25 (15–10)
Doubles: 25 (15–10)
Outcome Year_ Championship Surface Partner Opponents Score
Runner-up 2012 French Open (3) Clay Mike Bryan Max Mirnyi Daniel Nestor 6–4, 6–4
Winner 2012 US Open (4) Hard Mike Bryan Leander Paes Radek Štěpánek 6–3, 6–4
Winner 2013 Australian Open (6) Hard Mike Bryan Robin Haase Igor Sijsling 6–3, 6–4
Winner 2013 French Open Clay Mike Bryan Michaël Llodra Nicolas Mahut 6–4, 4–6, 7–6 (7–4)

Question: What surface was the Australian Open (6) played on for Bob Bryan's doubles: 25 (15–10) career stats?