These bar magnets measure about 1/4″ x 1/2″ x 3″ (72 x 12 x 6 mm). The magnets are made of Aluminum (Al), Nickel (Ni), and Cobalt (Co) which makes for a super strong and high quality magnet. Alnico bar magnets can be used with iron filings to demonstrate magnetic lines of force. The notched end indicates the North Pole of the magnet. These magnets are ideal for science fair project or experiments.