BuyMagnets.com offers small ring magnets made from grade 2 alnico, which has a maximum operating temperature of 1000 °F. Since grade 2 alnico is isotropic, it has no preferred orientation and can be magnetized in any direction. This magnet weighs just .001lbs, yet has a holding force of .094lbs. With a total diameter of .250” and a thickness of .062”, these small ring magnets can be used in the tightest spots.