... .size: OD 3MM-315MM 2.Light,medium and heavy any length solar vacuum tube & pyrex glass tubes3.3 size: from 3-315mm, and the ... of 37, 47, 58, 70 for the solar water heater.the high borosilicate glass tube enjoys good heat-proof, anti-rot, mechanical ... : ISO719-HGB17) Hydrolytic resistance at 121°C: ISO720-HGA1& any length solar vacuum tube & pyrex glass tube3.3