What the picture doesn't show is what a small and lightweight package these overtrousers pack away into - I was amazed when I opened the shipping bag! They are supplied in a mesh bag with a drawstring, which is roughly the size of a coke can (but a fraction of the weight, of course). What's more, unlike some products, you can easily fold them up to get them back into the carrying bag. The size is such that you can always have them with you in your pack while out walking.
The trousers themselves are very lightweight, with an elasticated waist, and easily pull on over your existing trousers. The material is pretty thin, so don't try to pull them on over walking boots, or you'd run the risk of tearing them. I notice Amazon don't show waist sizes: if it's any help to anyone, the "X-Large" size, which I bought, is for a 38"-40" waist (which, fortunately, is just right for me).
The material itself is completely waterproof but, as noted by a previous reviewer, there are slits in the sides to allow you to reach the pockets of your normal trousers, which could be a possible entry point for water. That hasn't been a problem for me.
All in all, an excellent product which I'd thoroughly recommend to any walker.