Eclipse Magnetics M17308/4NR Alnico Round Bar Magnet, Maximum Pull of 0.35 lb, 4" Length Round Bar magnets made from Alnico Grade 5 material, unpainted in color gray and have a maximum temperature of 550 degrees C Length tolerance is +/- 0.045", diameter tolerance is +/- 0.032" 1/8-inch diameter, 4-inch length Maximum pull of 0.35 pounds