B16a pistons can be either PR3 or P30. P30 pistons are from the JDM b16a that has 10.4:1 CR, PR3 come from all US B16a's or 1st gen JDM B16a's that are 10.2:1 CR. I've read that there have been some people that have measured CTR pistons and there is a big difference design between a ITR, B16, GSR piston vs. CTRs. CTRs actually will sit taller in a block and will yeild a higher CR than most people think. I think I remember hearing CR with a B18C5 and CTR pistons with stock bore is closer to 12.4:1, according to Omniman.