Heavy-duty magnets work well on file cabinets or metal presentation boards. Heavy Duty Magnets are three times as strong as standard magnets. Assorted colors include red, yellow, white, blue and green. Each pack contains 30 magnets: 12 small (5/8" Dia.), 12 medium (1-1/8" Dia.) and 6 large (1-1/2" Dia.) Magnets are packaged in a reusable tub.