Nite Ize 2-Mode Light Up Red LED Light Dog Collar - Red (1 x CR2032/Size-L)

Pros: Collar is made of some kind of nylon and plastic illuminated portion of the colored LED diode at the end. The whole thing is solidly constructed and can be clipped to the leash.
Together with the dog is very well visible in the night and clearly visible on a cloudy day.

Cons: The only con is the lack of protection against water - do not know how it works on the rain, but rolling in the snow can cause her time off.
It could be cheaper...

Other: One piece is enough for a very long time.

Pros: It's a really good dog collar, a really good safety thing because the dog is visible from afar. A big plus is that you can choose a flashing or constant light on the dog collar, another good thing is that it is reflective tape sewn into the collar so your dog can also be seen in the glow if the battery runs out. According to the package should be water-resistant collar,the collar is easy to turn on and off.

Cons: The only downside I see is that the collar is a bit too expensive to buy.

Other: Perhaps a little too expensive collar, but a very good and well built collar if you want the dog to be seen in the dark.