The BackBone DF2 is a bow-to-stern frame for the Advanced Elements DragonFly 2XC and Lagoon 2 inflatable kayak, which enhances both rigidity and performance.
The backbone should be an included accessory for all AE kayaks. Unfortunately it's not but it's essential. I almost returned my AE kayak because of it's slow performance but the backbone made it up to par with the hardshell kayaks. I don't think I would kayak without it anymore so suck it up and just buy this. I'll give it 4 stars since it's just a rigid pole that anyone can brew up at home although I admit it's pretty good quality though.
Worth it! We tried the Dragonfly with and without the backbone, and both of us noticed that with the backbone, we didn't have to work as hard to make speedy progress. It sits on the floor, but you can't feel it through the inflatable seats at all. In fact, it seems to help prop them up, which is a plus.