Promotes good squish. Read that as mixture motion which aids quick burn rates. I would be looking for high silicone pistons to control expansion. Pistons exexpexexpand not just on the diameter, but vertically. The 2618 aluminium pistons will expand more vertically than the high silicone pistons. Then you need to consider intended max RPM, which agrivates rod stretch. A light piston offsets that.
