... resist high temperature 2.contain no heavy metal. 3.high light transparency. colored borosilicate glass tubingUsuage:1.solar vacuum tube. ... colored borosilicate glass tubing Features:1) Available colors: clear , dark blue, light blue, amber, light yellow, green, pink, purple, red and opaque black ,opaque ... in glass tubing, glass pipes, waterpipes and so on. DARK BLUE Borosilicate Colored Glass Tubing