Works well and is great value.
This works really well, lay it black side up in the sun for a few hours and you've got 20 litres of comfortably warm water to shower in. Even better, lay it on the bonnet of your car after a journey with the the black side up and recycle the waste heat from the engine as well as picking up free heat from the sun (works even better if the car is black too).
The stopper could do with being better designed and would enable it to be used as a water pillow at night if it had a secure screw top.
Also, keep in mind that it will weigh twenty kg when full and that you'll need to lift that above head height to get sufficient pressure if you shower standing up.
All in all, a great piece of kit at a bargain price.