I'd called around and the lead shot at local gun shops are very expensive, most of them wanted about $6.50/lb depending on size. I did a search online and found most scuba shops also carry some lead shot pouch vary from 1 to 10 lb to help diver sink, If I remember correctly it's call the Sea Pearls Soft Weights. They're selling for $2.50/lb so I bought 20 lb, the shot are way more expensive than sand but they're very dense and heavy!! each VTI RF stand have total of 3 tubes and each tube can take about 10~12 lb so for now I only filled the center piece, the shot is small and very easy to fill through the hole. :-)
