Weight, size and quality are the key attributes of a good pack-a-way waterproof jacket.
Weight: 315g (XL size)- not much more than a can of energy drink.
Size: Packs easily into its own mesh bag measuring 20cm x 12cm diameter (or less if it's squashed down to remove the air).
Quality: Material is 100% polyamide with PU coating. Seams are stitched with internal tape welding to ensure waterproofing. There are two outer zipped waist pockets, integral hood with drawstring (the hood rolls into a velcro fastened flap when not in use), elasticated wrist bands, and two very large internal pockets.
Important point to note is that the garment shouldn't be washed with detergents or fabric conditioners (it states this on the label) otherwise the effectiveness of the waterproofing will be reduced. Regatta recommend their own Isotex cleaner, but there are other suitable and widely available agents, such as `Nikwax Tech wash' and `Nikwax TX.Direct wash-in'.
As a carry-at-all-times sensibly priced rain protector this jacket is hard to beat. It wouldn't be my first choice when setting out in the rain, but that's not what it's designed for. It's small and light enough to be carried everywhere, without even noticing it, to avoid getting soaked in an unexpected downpour.