Expensive for what seems to be a plastic bag, which can be bought for 5p from Asda/Tesco etc. However, as my rucksack continues to let water in, I thought I would give it a try. Suggest you take the rucksack you want to cover into the store where your going to buy this to ensure you get the right size. It fits quite well over my 45l sack that I don’t fill to the top, however, if you don’t carry much, it seems to “crush” the rucksack. Not a problem until you want to wear it, and find that its pushed the contents into a ball that doesn’t fit nicely onto your back. Can’t comment on the waterproof-ness yet, as I haven’t cycled in the rain (that will happen soon I am sure!). Visabilty of this is great though, especially as its starting to get quite dark in the mornings.