Hv 4.5

I had one and I am going to be selling it on eBay this week. It is an improvement over the 6.5. The power and speed do increase, but nothing too huge. It can't even begin to compare to the Quark/8xl combo I have now. But, for a basically stock E-Maxx with a few drivetrain improvements, it is a nice drop-in no hassle system. If you're a power/speed junkie go with something else.