This is a rechargeable batter front light for your G Line, the key features are as follows: 
Mounts to your G line front fork 
Bright with up to a 500 Lumen output and daytime flash 
IPX7 water resistant rated 
It has a maximum rub time of 20 hours and is rechargeable with a USB cable (not provided)
Machined aluminium body 
Battery capacity - 650 mAh