please contact with us via our e-mail: lwarlwar at hotmail , com Hand shake calculators (LC1067) Model No.: LC1067 This 8 digit display calculator uses Faraday Principle of Electromagnetic Energy to operate. You will no longer have to buy replacement batteries for your calculator. This battery-free calculator is powered by shaking the calculator side to side.Shake the calculator so that the magnet slides through the copper coil in the visible chamber , and enough electricity is generated to operate .size of product :110x58x25cm packing: 200PCS, 58¡Á31.5¡Á24cm, G.W:14.1KGS