The say about 104 pounds. I've read on multiple different reviews, multiple different reasons. A couple reviews said it was mainly between the engines. A few said it was mostly the extra sound proofing. A few more said it was the front and rear overhang (5 inches total). But the only thing we really know is that the Fiat battery is 10 lbs heavier than the Miata's (thanks to Good Win Racing for weighing them).Hopefully. What are the weight differences between the two vehicles ??