These disks differ from the Moon Glow in that the glowing plastic disk that gives them the name has been replaced with a colourful disk of G-10 fiberglass, the same material often used for the scales of blades, and also circuit boards. These cheery disks have the same SOLAS reflective tape on one side as the Moon Glow, and mirror polished steel day-time reflector washers on the other side. You can see that the washers come in two times, a flat finish on the blue, and a beveled finish on the yellow. The difference being the ability to signal strongly in one targeted direction with the flat, or to scatter light in a wider angle with the bevel. Different designs for different users needs and abilities.
These are great little pieces, and I'm glad Spencer threw them into my last order for me to have a play with. I will be passing the goodness on, in that I am making birthday gifts of these two, and hopefully they will be enjoyed as much as I have in trying them out.