They work pretty well, but they will crack when folded at the same crease excessively. My favorite models are the ones made for hydration systems where the spout is off to one side. This allows for more convenient stowage. I currently have a 1L and a 2.5L platypus like this. The one liter with a drinking hose is especially handy for long, hot bicycle rides (road) where the traditional "roadies" generally frown upon camelbacks (I must maintain appearances!). The one liter just slips into a jersey pocket. The moral of the story is that it is very effective, very versitile and very compact! As for plain durability, Camelback brand bladders are by far the most durable. In fact, Camelback now supplies hydration systems for the US military. Camelback invented the "hydration system" industry and they lead it in terms of quality and market share by a healthy margin. Go to their website as this might expand your thinking... www.camelback.com<br><br>