1/4" x 1/8" x 1/4" Rare Earth Cylinder Magnets from Magcraft. Set of 25. These cylinder magnets are 0.250 inch (6.4mm) outside diameter, 0.125 inch (3.2mm) inside diameter and 0.250 inch (6.4mm) long. They are magnetized through the length. They are composed of grade 40 neodymium iron boron magnetic material and are plated in nickel-copper-nickel for a shiny corrosion resistant finish. Maximum working temperature is 176 F (80 C).