Filling hollow tubes of my component racks

I used cat litter in my Skylan stands but didn't really seem to do much so I took it out. I couldn't get the Star Sound for a long time because their supplier went out of business suddenly and they had to find another. I have not done a scientific test because the Micro Bearings are so small I only want to put them in welded stands. Right now I have them in 15" Target stands I use with Spendor SP1/2s. I have the Atabits in a pair of 20" Atacama stands I use with Mini Utopia Focal speakers. I like the Micro Bearings because they seem to be the most effective is damping the resonance of the steel stands, VERY heavy for their volume. I was using lead shot but I thought it caused a coloration in the sound I don't hear with the MBs. Just my impressions. The MB seem even heavier than the same volume of lead shot, I haven't measured this and both are heavy. Lead is, of course, considerably heavier than steel but the MBs are much smaller than the lead shot so you can gat many more into the same volume.

Stanwal my thinking was clay has no sound of it's own similar to lead(which I don't want to use) and that most metals have some inherent sound they bring to the mix. I thought clay with some stone mixed in for higher weight might be relatively coloration neutral.

The basic question in my mind is how they act to damp vibrations. With very dense material of the smallest possible diameter the waves will be propagated to the smallest distance before being dissipated. I think that is how the "sound" of the material comes about. I did not think that that cat litter I was using was especially effective at absorbing vibrations so I quit using it. I would question whether the stone would be very effective either but the expense should not be too great if you want to try it. I have no problem using lead, did so for years and still have some but like the others better. I would check out the steel blasting shot if you are in an area where it would be readily available. Get the smallest diameter if you get some.

The metal that is heavier than lead volume for volume , thus you mean higher specific gravity is ... Tungsten.
It is not cheap but denser than lead. I imagine that an alloy is used because Tungsten is costly.
I am cuurently thinking of making my own version of magnetic levitators strong enough to supporta pre amp. I think the magnet strenth must by definition cause interference and whatever electrical grunge is AKA EMI. but you can get strong neodynium discs easy enough at a price that is not all that much.
I had already planned a needed not just for fun real vibration isloation solution but...
My prepaid never made sandbox is stuck in the hands of it's maker . I hoped to use memory foam from an upholstery shop. I am being very serious here that stuff is incredibly effective. Add some Bear paw footers and you can set the whole rig on the foam . I was hoping to get some 2 inches thick and make a micropure ? tungsten shot? sandwich.

I had put childs sandbox sand and buckshot in mine when I had that type of rack.