10 x 5 x 3 mm N52 Super Strong Block Magnets Specification: Dimensions: 10mm x 5mm x 3mm thick Tolerances: 0.2mm x 0.2mm (0.01in) Plating/Coating: Ni-Cu-Ni (Nickel) Magnetization Direction: Axial (Poles on Flat Ends) Max Operating Temp: 176ºF (80ºC) Pull Force: approx. 3.5 LB Surface Field: approx. 4500 gauss Material Features: Magnets are made of a brittle material. These magnets are not as strong as steel. They are more like a brittle ceramic. If you let two magnets slam together, they can crack and break. This is true for magnets large and small. WARNING!!! Strong magnets should Keep away from Ironware and some easily magnetized iron products, such as monitors, bank cards, computers, televisions, mobile phones and other. These magnets are very powerful which should be handled with great care. Without parents supervised do not allow children to playing magnets as they could get injured. Especially pay attention to the small magnets, please place in somewhere children can't reach place.