Magnets made from at least 2 materials, usually a magnet material in a steel housing.

This is done:

• to make magnets with threads or fittings. Magnet material itself is usually too brittle or difficult to work
• to create 'pot magnets'. These provide a more powerful grip when in contact with a ferrous surface than standard magnets
• to provide protection to brittle magnet material

Pot magnets are ideal for clamping and holding applications.

They have both poles on one face of the magnet. This allows a complete magnetic circuit to be made when this face is in direct contact with something magnetic, providing a stronger grip.