Feature: 1. Can be used in a variety of industries, such as audio equipment, electrical, electronic, mechanical equipment, healthcare and other industries. 2. Super strong Rare-Earth magnets, they are hard to separate once they get stuck with each other. 3. Perfect for sticking notes on fridge doors. 4. Suitable for DIY projects, such as white board fixing, adsorption of various steel parts, fixing tissue box on the roof, etc 5. Used for magnetized wax, pipe descaling, magnetic fixture, magnetic lock, door and window magnet, magnetic suitcase, leather magnetic toy, magnetic tool, gift wrap. Specification: Item Type: M4 Counterbore Magnet Optional Model: D15x3, D15x5 M4 Counterbore: Small Hole Diameter 4mm / 0.16in Large Hole Diameter 8mm / 0.31in D15x3 specifications: Diameter: Approx. 15mm / 0.59in Thickness: Approx. 3mm / 0.12in D15x5 specifications: Diameter: Approx. 15mm / 0.59in Thickness: Approx. 5mm / 0.2in Application range: Audio equipment: speakers, receivers, microphones, alarms, stage sounds, car audio, etc. Electronic products: permanent magnet actuator vacuum circuit breaker, electromagnetic relay, sound level meter, reed switch, sensor. Electrical field: VCM, Compact Disc / DVD-ROM, generator, servo motor, micro motor, motor, vibration motor. Mechanical equipment: magnetic separation, magnetic suspension, magnetic machinery. Healthcare: MRI scanners, medical equipment, magnetic health products, etc. Other industries: magnetized wax, pipe descaling, magnetic fixtures, magnetic locks, door and window magnets, magnetic luggage, leather magnetic toys, magnetic tools, gift packaging.. Package List: 20 x Magnet