1Provide 6 kinds of thickness (0.3/0.5/0.8/1.0/1.2/1.5MM) for you to choose. 2Thermal conductivity is up to 401 w/mk, very nearly silver's thermal conductivity 409 w/mk, much higher than ordinary copper pad (20-30w/mk) 3Exposed to the air, the copper surface will inevitably oxidize and turn dark, but the cooling effect does not be affected. If you still worry about it, you can polish the surface of this copper shim by fine sandpaper or toothpaste. 4Can solve laptop frequent crashes and other problems caused by thermal conductivity. 5Can be applied to the desktop computer north and south bridge connection, graphics card thermal conduction. Features: 1. Provide 6 kinds of thickness (0.3/0.5/0.8/1.0/1.2/1.5MM) for you to choose. 2. Thermal conductivity is up to 401 w/mk, very nearly silver's thermal conductivity 409 w/mk, much higher than ordinary copper pad (20-30w/mk) 3. Exposed to the air, the copper surface will inevitably oxidize and turn dark, but the cooling effect does not be affected. If you still worry about it, you can polish the surface of this copper shim by fine sandpaper or toothpaste. 4. Can solve laptop frequent crashes and other problems caused by thermal conductivity. 5. Can be applied to the desktop computer north and south bridge connection, graphics card thermal conduction. Specifications: Material: Copper Size: 20(L) * 20(W)mm / 0.79 * 0.79inch Thickness: 0.3, 0.5, 0.8, 1.0, 1.2, 1.5mm Quantity: 10 Pcs Package List: 10 x Copper Shim