This is pretty interesting! I wonder what goes into the components and if you could rig up a DIY version (that didn't rely on plastic imported from China)...
You'll have access to light, anywhere! The GravityLight is a non-electric solution that uses an elevated weight on a pulley system that slowly powers a generator as the weight falls to the ground, providing you with usable light. No batteries or sun needed, just hang it up and fill the bag with rocks or sand (about 26-1/2 lb).
Affordable, safe and eco-friendly!
Provides 20 minutes of light as it descends; just lift for more light
Gives you instant light (15 lumens), no running cost
Since no batteries are used, you can store the light indefinitely - no worries of batteries degrading
When installed, it provides a 6 ft drop of about 26-1/2 lb (12 kg) weight
The pulley system makes it only feel like about 6-1/2 lb (3 kg)