SRT piston was 1st developed for our B-Mod program allowing them to make better traction off the corner when the track is rough. We have been able to do this by allowing bypass thru the piston when the car is on the bars and traveling across a rough surface. Since we have introduced this piston it has allowed us to developed other shocks like the Air Shock and the Bypass shock. The SRT is becoming more and more popular of a choice when people decide to buy shocks even on a smoother surface as it allows the car to make more traction to the tire. We are releasing this as an option for a piston upgrade to as standard shock such as a 15, 20 and 25 Series Shocks in both base valve and non base valve shock. The SRT piston is a $50.00 dollar upgrade along with the standard $30.00 dollar labor fee for servicing a shock, we can do it now or at the end of the season when we service your shocks.