Glow sticks and reflectors are there so that others see you in the dark and so that you can keep track of your group. A chemical stick needs no battery and no switch: bend it, shake it, and it burns for hours. Reflectors give off no light of their own – they send someone else's light back, so they work only when something is shining at them.
The range holds M-Tac and Helikon-Tex sticks, an elastic reflective armband and Velcro patches for a helmet or a pack.
It depends on the model and the colour – usually between a few hours and twelve. Once bent it cannot be switched off, so break it only when the light is genuinely needed.
A reflector is visible only in the beam of a torch or headlights, because it returns light aimed at it. A glow-in-the-dark patch emits the light it soaked up during the day, so it is visible without any source – but much more faintly.
