On theme with C2’s interchangeability, models D or E are essentially the same machine. When we talk about one we’re talking about both. The Concept 2 E is just 8 pounds heavier but is made out of stronger stuff all around — what’s plastic on the model D is aluminium on the model E, and what’s aluminum on the model D is welded steel on the model E. The only noticeable variations are seat height and display position.
The rowing machine itself is unlike any other on the market with its patented water filled flywheel. It is hard to exactly copy the action of a scull on the water, but the mechanics of the flywheel spinning in water comes in a close second on dry land. The fact that the water is 800 times denser than air means that there is no need for any extra resistance or dampening that you will find in normal air rowers. The faster you pull, the more resistance is generated giving it infinite variability. However, if you want to be able to practice rowing with a faster stroke, you will have to reduce the amount of water in the tank unlike an air rower where you just have to adjust the baffle.