Leather Seats - Just the sitting surface?

Kenwoodturbo

I don't know for 370z but many cars are this way and you can't tell with naked eye. The bolsters on sides and bottoms are usually a synthetic material. I've had gm, Toyota, honda, and fords that were this way. My guess besides cost savings would be that the synthetic hold up better to getting in and out of the car. Thus less complaining from customers trying to get warranty repair for messed up leather from sliding in and out of the seats. In cars where I knew this was the case I could not really tell by looking wih naked eye. You could feel it after conditioning. Or see it when magnified. Typically you can tell by the way they advertise the leather option. Verbiage will read "leather appointed" seats.