When we first saw the Firefly, we thought it was a cool idea. Now that we have had a few days to play with it, we think it is a brilliant idea. The Firefly will fit over any wide-mouth container and turn it into a lantern. The brightness level is adjustable by holding down the On/Off button. The amount of light given off is surprising considering the size of the LEDs in the cap.
The cap is a self contained unit (batteries, LEDs, switch, tether) and is very portable. It's powered by 3 AAA batteries sealed in the cap.
The battery compartment is protected from moisture by the rubber gasket (red arrow) and a channel on the cap. When the lid is screwed down, the channel will pinch the gasket to seal out the elements.
The tether loops around the opening of the container and is secured by clamp. The one drawback is a hex key is needed to make any adjustments. Since a key is needed, it also would have been more convenient if the screws (Philips) on the lid used the same key for fastening.
The tether is a strong 4mm nylon rope and will last a long time. It is just right for hooking a carabiner to it to make the bottle easy to hang.
Click on the videos below to see the Firefly in action. Note the change in brightness as we cycle through the different settings.
The only other improvement we would ask for is if they could figure out a way for us to access the water without having to unscrew the cap...so we would finally stop knocking over our glass of water at night :-)