The most common places you'll find magnets include:
Bicycle dynamos.
Crafts, hobbies and jewelry.
Paper crafts, scrapbooking, album making
Computer hard drives.
Health bracelets, bandages and other medical devices.
Magnetic resonance imaging devices.
Wind turbine generators.
Fishing reel brakes.
Permanent magnet motors in cordless tools.
High-performance AC servo motors.
Traction motors.
Integrated starter-generators in hybrid and electric vehicles.
Mechanically powered flashlights which use magnets for generating electricity from a shaking motion.
Industrial and testing/quality control applications such as for verifying and maintaining product purity and equipment protection and integrity.
Linear motors used in mag-lev trains and other motorized model equipment.
Scientific applications such as diamagnetic levitation experimentation, the study of magnetic field dynamics and superconductor levitation.
Electro-dynamic bearings.
Roller coaster and other thrill ride technology.
Magnet toys.
Audio speakers and headphones.
Electric guitar pickups.
Miniature figures and models.

Sold in Matched Pairs
Each set of countersunk ring magnets includes 10pcs with the countersunk hole on the north pole, and 10pcs with countersunk hole on the south pole. This allows you to pair them together to create magnetic latches, fasteners, and other closure mechanisms.