The piston is the weak link in the stock STI block. By adding these forged pistons to your stock STI block you are able to get 500+ hp out of the motor. These pistons are +.020 bore.

Features include:

High Strength Aluminum forgings

Super Lightweight designs

Fully CNC Machined and balanced to +/- 1 gram

Wrist pins included

Accumulator groove included

double pin oilers, force fed from oil ring

pick lock grooves for easy lock removal