Ronhill Bright LED Flashing Light Armband for running & cycling is lightweight, compact, durable and shock resistant. The ultra bright LED can be set on flash or permanent glow, it is easy to turn on/off and will still act as a reflector when turned off. The batteries last for 70 hours on permanent or 100 hours on flash and are easy to change. This weather proof road safety device is lightweight at only 40 gms ( 1.4 oz ).