I have been running a White Bros E-Series can and headers on my XR650L supermoto for about six months. I decided to try the new E2 can with my existing header, so I ordered one. As I unbolted the two frame bolts on the E-Series can, it literally fell apart in my hands. The can fell off, leaving the S-bend pipe still stuck into the header. It had fractured the weld all the way around the pipe! I put the E2 on. It's VERY different than the E-Series. First, it's longer and sticks out the back farther. It mounts to the frame at the S-bend like the stock pipe and the E-series, but the upper rear mount is at the fender bolt, rather than the stock exhaust mounting bolt. It also does not use a gasket or a clamp between the header and the S-bend, WB says it is designed as a slip fit, and so far anyway, it works. No leaks at the junction. The E2 is aluminum, nicely machined, and is a "square oval" cross section. That shape plus the length gives it more internal room for packing. The core is very large, as big as the S-bend all the way through. It comes with a 96db USFS approved spark arrester. They also supply what they call the Competition insert, which is just a machined aluminum cap that fits in the end and preserves the full diameter of the core all the way out the back. One allen screw with a 4mm head is all it takes to switch between the two inserts. It's *extremely* loud with the Competition insert. Too loud for me, and I kind of like loud thumpers. It also flows so freely with the Comp insert that I think it would have to be rejetted accordingly. I did not try rejetting it because it's simply too loud for me. It's *very* quiet with the spark arrester in, and having tried it both ways, I prefer it quiet. It has excellent power even with the spark arrester in, so I'm going to leave it that way. The E2 seems noticably lighter than the E-Series too. So far, I'm very pleased with the E2.