GSC Power-Division S1 camshafts for the EJ205 WRX Version 5 and 6. These cams are built to suite the high horsepower Subys. With a power range of 500WHP and up, you need some certain mods to utilize the true potential of the S2s. Built motor, with a built/ported head, and a good engine management system. Dual valve springs are recommended, but a upgraded single spring kit will do the job under 8000 rpm.