The new Erzberg 550 is an updated version of Ogio's previous hydration pack, and the product features several improvements over the old unit. For one thing, the bite valve has been redesigned so that it no longer ends in a 90-degree angle; the new version is much less prone to getting caught up in branches and throttle cables. I did have the bite valve freeze up on me during a sub-zero snow bike ride, but I found that blowing back into the tube after taking a drink and also chewing on the rubber a bit periodically all but eliminated this. The reservoir bladder remains easy to clean (you can turn it inside out), and I was pleased with the 70-ounce capacity. Usually, my bike ran out of fuel just before I ran out of water--as it should be!The pack itself is Spartan in design, with only one zippered outer pocket in addition to the reservoir compartment that is just large enough for a pocketknife, a few granola bars and a set of keys. Design-wise, I was a little bummed the zipper on the outer pouch zips up rather than down, because it wasn't uncommon to return to the truck after several hours of pounding trails only to find that the zipper had worked its way down an inch or two. I found that a small carabiner attaching the zipper to the hanging loop took care of this issue. I should also mention the zippered access to the main compartment--which serves as a guide for the hose and runs all the way over the shoulder and down to the end of the strap--limits routing of the hydration tube to the rider's right-hand side. I typically run my tubes on my clutch side for easier drinking while on the gas, but with the 550 you don't have a choice.