Button Magnets are simply horseshoe magnets in a compact circular format. They are made from Alnico to provide a high resistance to corrosion and a high temperature rating. All sizes have clearance holes for mounting. They must not be recessed into ferrous materials as it will short circuit the magnetism. Maximum operating temperature: 500°C.The E-Magnets 824 Button Magnet has the following specifications: Diameter: 32mm (1.1/4 inch). Height: 25.4mm (1 inch). Maximum Pull: 4.8kg.