3" Dia x 1" Thick, (1.75" hole) NdFeB Ring Magnet, highest grade available, Ni-Cu-Ni Plated with Matte finish, Axially Magnetized (the top & bottom flat faces are the north & south poles). Theoretical maximum pull: 230 pounds.
This magnet can be used to replace the coil of wire inside a regular GM 10SI or 12SI alternator, to convert it to Permanent Magnet operation.