Suggestions for filling speakers stands?

Silicone (but not sand) is better than steel shot and steel shot is better than lead shot as far as passing mechanical energy. Brass is the most capable, but where ya' gonna find brass balls? Oh, i know :) I can't say which would be best for you rig, though. Gotta experiment

I know there is someone who sells silicone in audio form, but i have forgotten who they are. The only other place i can think of is a pool table/bar-games store. Some of these stores sell those long wooden tables where you try to slide a puck in to a defined area for points, like shuffleboard. These tables use silicon sand for the puck to slide over, and of course the store carries the 'sand' ( in a very fine form). Looks like Albert has found a less expensive sorce, though, there's no way you're gonna get a 25lb bag for $21 at these stores. I use the word 'silicone' meaning a "solid", but i am not sure whether that variation of the base word specifically refers to the more liquid form instead. I'm not absolutely positive, but silicon probably has the one of, if not the highest, energy-transfer/density ratios of the materials used by audiophiles. If i do think of that audio company, i will let you know.