I have just bought some from Ebay. The seller has given me permission to reproduce his write up. For your information I enclose it below.
Neodymium Magnets, mini size. 4 x 0.5mm Disc. Qty 50
Item number: 130167222243
If you have not heard about NEODYMIUM MAGNETS (NdFeB) or RARE EARTH MAGNETS as they are also known, then you are not alone. These are the strongest NATURAL magnets as yet known to man, more than 10 times stronger than the equivalent sized ceramic magnet. They are PERMANENT and will not decrease in strength for your lifetime, no matter how old you are!!! They do not require a 'Keeper' Bar like old style magnets, and they are amazingly strong, sometimes beyond belief. The large sized ones have a multitude of serious applications, the smaller ones are both extremely useful and heaps of FUN!!!!
WARNING: Please read and Be Careful!
All magnets have certain risks and dangers associated with them. These NdFeB magnets are much stronger than magnets most folks are used to, so even a seemingly small magnet could be full of surprises! Small NdFeB magnet pose little risk, although one should be careful around electronics and magnetic storage medium - especially if you're handling a large stack of them!
Pinch Hazard: Larger magnets (NdFeB magnets larger than a 5p) are strong enough to pinch fairly hard should one get his/her fingers in between two of them, or between steel/iron and a magnet.
They are Brittle: These magnets are brittle. Should two magnets snap together hard, or snap onto a ferrous surface, they could break or chip.
Electronics and magnetic storage medium: Magnetic fields can temporarily, or permanant damage certain electronic devices and magnetic storage medium. Keep them away from computers, computer monitors, cassette tapes, floppy disks, etc. With smaller magnets, you should be safe if you keep them at least 3" away. But again, if you have a large stack - a little extra care and distance would be appropriate.
Health Risks: There are no known health risks to handling magnets EXCEPT: Certain pacemakers or any other electronic health devices could be affected. Don't handle magnets if you wear a pacemaker or any other electronic health device unless you get your doctors approval! Pregnant women should probably avoid strong magnetic fields.
Like any other potentially dangerous item or substance, these magnets are perfectly safe when treated with care and stored properly. Treat them with the same respect you would power tools, knives, ammunition, etc. Your magnets (unless they're small refrigerator magnets) should be kept in a safe place away from electronics and out of the reach of children. Properly stored and carefully handled, these magnets are perfectly safe and should last a lifetime!
Should stop me loosing hatches.
Cheers...Ken