The other day I was asked by the JDM H22A produces more HP than the USDM H22A1. These pictures should help answer that question.

USDM H22A1 Piston:


JDM H22A Piston:


Both Pistons:


Look how much larger the dome is on the JDM piston than the USDM piston. I have a set of JDM TypeS pistons on the way, once they come in I'll compare those two the JDM H22A and USDM H22A1 pistons. I'll measure the domes to see how much of a difference they're actually is. This is just a little FYI. If you have any questions, please feel free to ask.

-Mike