
The light with key chain weighs in at 21g and with key chain removed it weighs 18.5g.

I have not used the Dynamo Keychain Light in field testing yet and probably won't until warmer months but in testing at home on less than a minute of winding the light stays very bright for about five minutes and then stays bright for about an hour, this is enough to cook by or get changed in a tent, and probably enough to walk a long a reasonably good track, after two and a half hours there is still some glow in the LED's but not enough to do much by.
This torch a wonderful idea and very light but is probably not suitable for mood lighting. I normally use a head torch as I like to have hands free when cooking at night, I will work on a head band system to attach to this torch too.
Tony