SET INCLUDES one red alnico horseshoe magnet (1 inch high)--that holds up to 4 lbs--plus a keeper. Remove keeper before use. Store with keeper in place, which helps this magnet "keeps" its magnetism! ALNICO MAGNETS are heavy duty magnets made of Alnico 5 metal material: ALuminum, NIckel, and CObalt (AL-NI-CO). Permanent magnets have greater strength and durability than many other kinds of magnets. STRONG MAGNET: Alnico horseshoe magnets position the north and south poles close together, creating a powerful magnetic field between the two poles. This allows them to hold more than a bar magnet. FOR KIDS SCIENCE EXPERIMENTS: Explore polarity, attraction, and repulsion. Great for hands-on science investigations, STEM projects, classroom labs, science fair, science clubs, home school, and more! SAFETY AND DURABILITY: Super strong magnet (durable classroom magnet) is designed in the USA by Dowling Magnets, experts in magnetic teacher supplies/classroom supplies. Safety tested for ages 8+.