MONTMELO, Spain -- Force India, Toro Rosso and Haas unveiled their new cars for the 2018 Formula One season shortly before preseason testing began on Monday.

Sergio Perez and Esteban Ocon pulled the tarp off Force India's pink-and-white car, dubbed the VJM11.

Perez and Ocon return for Force India after a good 2017, when the team finished fourth in the standings behind Mercedes, Ferrari and Red Bull.

Brendon Hartley and Pierre Gasly, who made their F1 debuts last year, did the honours for Toro Rosso's STR13.

Romain Grosjean and Kevin Magnussen also return for Haas, which finished eighth among the 10 teams last year.

Testing at the Circuit de Barcelona-Catalunya runs until Thursday. A second four-day session will be held from March 6-9.

The season-opening Australian Grand Prix is on March 25.