Practical Design Our black magnetic hooks heavy duty have been upgraded for generations. Now we use the high grade NdFeB material, A3 steel shell as the basis. So the pulling force of the strong magetic hook is higher than other products of the same size. The maximum working temperature of neodymium iron boron magnetic is 176 F (80 C). They are amazingly wonderful for their size and have innumerable uses. Data Based on Scientific Measurement Vertical Tension: 22 lbs Horizontal Tension:8 lbs 1.We used A3 high quality steel as the test floor. 2.After many measurements, we have obtained scientific and rigorous measurements by pulling the hook at a uniform speed on professional equipment. Several Important Factors Affecting the Tensile Force of Magnets 1.Only when the thickness of the tested steel reaches a certain level, the magnetic flux through its cross section would be the largest and the leakage magnetic field between the magnetic poles is the smallest, the tensile energy can reach the ideal value. 2.Only when the force is perpendicular to the contact surface can the tension reach the maximum. When the force is parallel to the contact surface, the pulling force can only reach 1/3 maximum. 3.Magnets hooks attract only magnetizable materials such as iron, cobalt, nickel and their alloys. It can not attract non-ferromagnetic plates such as aluminum, copper, wood, plastics and stainless steel. 4.The farther the magnet is from the magnetic material, the greater the leakage magnetic field and the smaller the pull force would be. Therefore, the surface paint adsorbed by magnets is also an important factor affecting the pulling force of magnets. WARNING Keep away from iron and easily magnetized objects, such as monitors, bank cards, computers, televisions, mobile phones, etc.