If you have to fit your training training runs in after dark this little gadget is the best six pounds worth of gear you will ever spend. It weighs virtually nothing but gives a good beam of light six to eight feet in front, allowing you to avoid puddles, ice patches and all the usual hazards. I wear mine clipped to the peak of a cap but it also has a headband, allowing it to be worn under the cap if it's raining ( it is described as water resistant ). The two coin-type batteries last many hours and replacement packs of twelve are very cheap anyway.Panasonic Specialist Lithium Coin Batteries CR2016 x 12
BTW, if you run with your mouth open look out for moths attracted to the bright light!