These countersunk ring magnets are 0.750"(19.1mm) diameter x 0.200"(5.1mm) inside diameter x 0.125"(3.2mm) thick. They are magnetized through the thickness. They are composed of grade 40 neodymium iron boron magnetic material and are plated in nickel-copper-nickel for a shiny corrosion resistant finish. Their individual pull force is approximately 5.8 lbs. Maximum working temperature is 176 F (80 C).