Single bases using metal washers

[O Dinas Powys]

Also, they're magnetic enough to stick the bottom of an old tin and easily withstand spraying with a can of primer:

[Corso]

Checked last night and the 12mm disks are 1mm. 

Couldn't find any of the 25mm ones, but I think they are probably punched from the same material.

Cool my 6mm project used 10 and 15mm magnets but I need something bigger for terrain

[O Dinas Powys]

Cool my 6mm project used 10 and 15mm magnets but I need something bigger for terrain

The disks are made from the same material you can get in sheets/rolls.  I've tended to use rare-earth magnets if I need anything more substantial to stick, but a few of these would probably do the trick.

[Last Hussar]

12mm is 1mm?

Is this some kind of Zen?

[O Dinas Powys]

12mm is 1mm?

Is this some kind of Zen?

We are all but vectors in an n-dimensional hyperspace... 

[Corso]

The disks are made from the same material you can get in sheets/rolls.  I've tended to use rare-earth magnets if I need anything more substantial to stick, but a few of these would probably do the trick.

It's 6mm scale one per piece should work 

[O Dinas Powys]

It's 6mm scale one per piece should work