The thermal conductivity set comprises four metal bars held firmly together in parallel with a plastic rigid carrier.The metals are copper aluminium brass and steel.Each bar has a Liquid Crystal temperature sensitive strip attached and its conductivity value marked on the back of the carrier. The liquid crystal strips have 8 boxes and change to a green colour at about 40°C.What the Colours Show:The thermo-chromic Liquid Crystal used in Conductivity Bars shows temperatures in the range 35°C to 45°C. The lowest temperature indication is a coppery red colour at 33°C and the hottest is a blue colour at over 45°C. The 35°C to 45°C appears in green.