the double button system, which is an industry first, allows you a choice of settings for different conditions. the upper button is perfect for dry or concrete starts while the lower button is suited for tacky conditions.  the double system allows you a choice without changing fork guards.  as starting line conditions change throughout the day and from track to track, the fly racing double button has you covered.  very cool design and man, does it work while still maintaining the same cost as the competitor's single button system.