The Malaysian race was the first at which the tyre compounds used on the cars were differentiated by a white stripe painted in the tyre treads. Since the beginning of the 2007 Formula One season, teams had been obliged to use two different kinds of tyre on each car during the race: a 'prime' tyre and an 'option' tyre. The prime tyre has a harder rubber compound and the option tyre a softer one. In general terms, a softer tyre is likely to grip better and provide a higher cornering speed. Conversely, a harder tyre will often be slower, but may last longer. Formula One cars typically use between two and four sets of tyres during a race and using harder tyres may allow fewer pit stops to change tyres. Track conditions, the car characteristics or driving style can reduce or even reverse these differences. In Australia two weeks earlier, the softer tyres were marked with a small white circle to facilitate understanding of each driver's tyre strategy, but commentators and spectators were unable to distinguish the two compounds even at slow speeds. The idea of the white stripe was tested during the test session a week before the Malaysian round of the season. The white stripe was applied with paint marker pens. Over the weekend 160 pens were used. Overall reaction to this system was positive, with the Williams team's technical director Sam Michael, who came up with the initial idea, calling it a "pretty good solution".