The more I think about what Tesla might do, the more I think that because the M3 has physically less room for batteries than the MS, there will be far less kWh delta between smallest to largest. I think that this means 2 physical configurations, but MANY range tiers/selling opportunities (via software). So I think that the 2 physical configurations will be 60 and 75. There will be a 55 kWh model eventually, when Tesla finally offers a $35k M3 sometime next year just to check that box. The 55 kWh car will use the 60 kWh pack and is a loss leader for Tesla that will have limited availability and popularity, it just checks the $35k and 215 miles box, but not very common. So the 60 is used on the 55 and 60 and still gets tesla an opportunity to up sell the 55 folks later for more money with minimal exposure if they don't bite. Plus the 60 will beat the Chevy Bolt at introduction. Then the 75 is used on 65, 70,and 75 with future up sell potential on the lower 2. Finally, another tweak to my theory is they might use 70 as the 2nd size and only later introduce a 3rd physical 75 pack as something new once the car is established and they want to do something "next".