These are not real 'Skully' bike lights and even if they worked, would be inferior. The on/off button under the nose does not work on either piece. Whilst I am holding the button down, I sometimes briefly get flash mode which demonstrates the batteries have power. When they do flash, I can see these LEDs are not bright and have a blueish tinge, so are probably cheaper than pure white. It's a shame that they don't show the packaging on Amazon, since you can quickly gather from the spelling of 'SAFTY REAR LIGHT' on the front that these are cheap - and innacurate and sloppy - copies.