Priced as a pair these clips simply slide onto the back of your trainer. They clamp to the side walls and provide a very good way of being seen whilst running in the dark. They are robust and waterproof and do a really good job. The battery can be replaced with a small screw driver and once you have them you will wonder why you havn't used them before.
These can be seen from long distances and cen be set at flash or solid lights.
They are a great safety device and can be used on any foot wear.