My bad .... Guess I oughta read the whole thing. It didn't come with any nipples .... Ok then , the hole on the side would be the PCV tap. I don't know the exact size, but I know the PCV nipple has a smaller hole than the tank pressure nipple. I don't know if I helped you out any or just confused you more. You might get a better answer in the Glow Engines forum .. or at least a better explanation.