22 years old at the start of the season. This class is no longer in use in 2007. In 2006, testing was restricted to a maximum of 10 days per driver/car, with no testing at race venues, Consequently, teams and drivers have to make the most of the test sessions during race weekends, which had already been reduced from 90 to 60 minutes in 2005. Tyre usage is restricted to three sets per car for the entire race weekend. There is no limit on the use of wet-weather tyres, but only when they are deemed necessary by race officials. As is the case with most racing disciplines outside Formula One, tyre warming devices are not permitted. An unauthorised engine change during the course of a race weekend invokes a ten-place penalty on the starting grid. Event schedule Each race weekend begins on Friday, with one 60-minute practice session and a qualifying session that decides the starting grid for the first race. There are two races; one of approximately 100–110 km on Saturday and one of approximately 70–80 km on Sunday. The starting times of each session/race vary slightly according to the event schedule at each venue. With just one qualifying session, the grid for the second race is determined by the results of Race 1. The top eight positions are reversed, giving pole position to the 8th-placed finisher. The single qualifying session and results-based reverse grid system were introduced for the 2006 season: prior to that, the second race had its own qualifying session (with a bonus point for pole position). Drivers who fail to finish the first race occupy the remaining grid positions for Race 2 in the order in which they retired. Scoring system In the first race of the weekend, points are awarded to the top eight finishers, with 10 points for a win. One bonus point is awarded for the fastest qualifying time. In addition to the change to a single qualifying session, the points system for the shorter second race was revised in 2006: rather than award full points, it now awards points to the top six finishers, with only six points for a win. Chassis and engines Three engine suppliers joined the new championship at its inception: Mercedes-Benz, produced by HWA; Opel, produced by Spiess; and Toyota, produced by TOM's. A limited number of teams have competed with Renault and Mugen-Honda powerplants. In the