I recently did an Iron Butt run with 11 bikes total. even with my full face helmet I was able to drink whenever I wanted and it lasted for the whole ride. I had 2 bottles of water that I drank when stopped while eating granola bars, and I had a beverage with our one stop and sit meal, but other than that I was good to go.
It seems a bit lightweight in construction, but the price was awesome compared to other hydration backpacks.
The rubber mouthpiece you see in the picture contains no orifice for which water may pass. So, it must be removed, which leaves an open-ended-tube. And when you suck, water indeed passes into the mouth but now you've created a vacuum and the water does not stop flowing until you either pull your motorcycle over in traffic to put the rubber plug back on or, while riding, you take both hands off the bars and force the cap back on. Which is, of course, stupidly and unacceptably, non functional.
I bought 2 of these about 8 years ago (1 for me and 1 for my father). It's good for a tool kit, wallet, keys, couple of snacks, and of course, water. It has held up extremely well. Never left a crappy "chemical" taste like some people have said about other hydration packs. My one and only complaint is getting the bladder in and out of the bag is a bit of a pain but not unmanageable.
Fits well, has enough pocket space for few smaller items and maybe a tool or two. Maybe Im not doing it right but I had a little trouble to get a good fluid flow out of that sucking knob. Overall I recommend this item.