If you wanna know about these things, I don't think that they are actually
clay. You can buy them in Europe under the brand name 'Seramis'. I've not
used it in a potting mix, But they hold water well, so I use them for
creating humidity for my neps, without getting their roots wet. On the pack
it says that they are for use as on of those 'hydroponic' potting schemes,
or sumthink.
see ya
Bearo
Bearo (otherwise known as Charles J. Beare esq.)