This 4-pack of handy magnetic utility clips are strong enough to keep those important lists, memos and letters from sliding out of sight. A must for every studio, school, office and home. For use around the shop, home or office. Avoid the frustration of weaker magnets. More About Ceramic Magnets: Our hard ceramic ferrite magnets are composed of iron oxide and barium or strontium carbonate. Ceramic magnets exhibit relatively good holding strength for their price, making them a popular choice for many consumer, commercial and technical applications.