The moon lunar rear light is a must have and will keep you visible to the vehicles approaching you from behind the light comes supplied with a qr seat post mount which makes it super easy to attach and remove from your bike coming supplied with two cr2032 batteries you are able to remove the light from the packaging and use it straight away the two cr20132s last a whopping 67 hours on strobe and 75 hours on 50 flashing so you have plenty of time to stock up on your next set of batteries d