I have had a Tesla S since 2013, so I can share a little bit about the range perspective and cruising speeds from that perspective. Firstly, I will note that I never cared about rolling resistance of tires before have an EV and it does make a huge impact on watts/mile at all speeds, but particularly as you go over >65mph. On relatively level ground at 70mph, my Tesla S draws about 330 watts / mile (so each KhW delivers approx 3 miles of range). That efficiency goes down significantly >75 and at >80mph, I would be drawing at 450 watts / mile, drastically reducing range. You should have very good efficiency at 65 to 70 mph. I think they are proving the KhW necessary to have 300 miles range at 65mph on the standard battery pack. I think the standard battery back is going to be 130KhW, which means that if you maintain approx 425 watts/mile (their on board computer will show you efficiency), you would have that 300 miles of range. We can assume the R1T and R1S will have more drag than the Tesla Model S, but I would be surprised if either consumed close to 425watts/mile on general highway driving compared to the Tesla S, so I think Rivian might be hedging more battery pack great load capacity, light towing, increased drag, terrain (including more climb). Hope this helps.