Don't we wish more things in life had such easy directions? How could you go wrong with an arrow on top of the piston telling you what way to point it in the bore? Well, believe it or not, you can install them just the way they tell you and still be wrong. That's because they have to coordinate with the connecting rod. And since a piston can go on a rod either way, you have to make sure they are aligned properly. In Patrick's case, PAW had marked each piston/rod combo with an L or R, indicating what side of the engine it needed to go in.