solar vacuum tube High borosilicate 3.3glass.the life can lasts 15years. Manufacturer for more than 14years. solar vacuum tubeVacuum tube:1,the pipes are made of advavced superconductive oxygen-free copper heat pipes2,graceful appearance long service life and non pollution3,the evacuated tube with superconductive heat pipe is the most advanced product inthe world4,Dimension:dia,28*1200mm,dia,28* ...