Eclipse Magnetics M16479NR Alnico Ring Magnet, Maximum Pull of 1.3 lb Ring magnets made from Alnico Grade 5 material, unpainted in color gray and have a maximum temperature of 550 degrees C OD & ID tolerance is +/- 0.016", thickness tolerances is +/- 0.05" 1" OD, 3/4" ID, 1/2-inch thickness Maximum pull of 1.3 pounds