I bought my 650 Kandle LED for my ebook reader Sony PRS. Due to the previous reviews I was not quite sure if the light is sufficient for a 6 "screen. After first use, I'm 100% satisfied. Also, at the bottom of the light output is sufficient even at absolute surrounding darkness. I can but so far do not have any information on whether when the battery is running low, the light yield. Upon delivery but four more button batteries were also there!