Big John, they are glass, probably cut off a glass tube. Dyna Beads are "ceramic", probably of superior quality than the glass beads. However, since virtually anything including sand will work it SHOULD make no difference what the medium is, just so it "flows" freely inb the tire and does not destroy the tire.
Yes, they made a difference in the wife's Like which had an irritating road speed vibration. The vibration is less now but still there. I think what is left is due to Kenda tires lumpy treadform.
Will advise all as time progresses.
Karl