The eBay one seems to be a single direction speed controller that drives the two motors in the same direction. I guess 2 of those would work fine in a 4wd setup, but there are some cooler (£15 more expensive) 60a ones on hobbyking that I'm going to run in my new featherweight. Again, I'm getting 2 because they are single channel, but are good for my 4WD setup.