When we ere designing the Greenjacket we wanted to give it some additional protection compared to the rest of the jackets on the market. After paddling the protos and samples for a year now I'm a big fan of is the back "flo-tection," that's our name for this technology. Basically its a layers of Nylon, a layer of PE Foam with thin plastic surrounding it, covered in a layer of Cordura material on the outside for abrasion resistance. Its a bit beveled so that when you paddle or swim you don't even notice the padding being there. Its sweet to set your boat on when you're carrying. The idea is to protect the bony parts of the back, the scapula I think its called. I could really see this coming in handy getting flipped on a slide or being upside down in a boulder garden. The yoke (top) is a bit higher in the back than on the Aquavest 300 so you get some extra protection there as well. The sides also have flotection with 2 layers of Cordura, 2 layers of foam, and again the Ballistic material. The inner (lower) foam panel wraps the rib cage to meet the side wings providing additional protection for your ribs and organs.