The combo pack includes one each of the solar demonstration classics: radiometer and uv beads. These fun science items demonstrate solar energy concepts. The vanes of the radiometer absorb (black side) and reflect (white side) the energy of the sun. This action causes the vanes in the enclosed glass ball to spin. The UV sensitive beads change color when exposed to uv light (sunlight or black light). These beads can be used to conduct experiments or create bracelets and necklaces.