Low-cost, high output sealed Thermoelectric Peltier element measuring 40mm x 40mm, Peltier elements are thermo-electric heating and cooling devices that feature solid state,reliable temperature control, Popular Uses include cooling elements for mini fridges,dehumidifiers and cooling hot running ICs and Cpus such as those used in Computers,basically when connected to a DC power supply they will pump heat from one side of the element to the other meaning one side will get very hot whilst the other side will get very cold,by adding a heatsink and fan to the hot side (a necessity) to dissipate the heat the cool side will remain very very cold,varying voltages from 5v to 16v can be used,Manufacturers technical specifications are as follows,Max Watts 37,Max Temperature Differential 75 degrees C,Max Amps 3.9,Max Volts 15vdc,Peltier elements can also be used to generate free electricity simply by heating one surface and cooling the other, With a sufficient temperature differential a cell can output up to around 1 Amp at 5V ,more than enough to charge small batteries or drive a small electric motor,these things literally have hundreds of different uses and are great for experimenting with,Please Note,these peltier elements are moisture sealed around the edges to prevent any corrosion over time.