Borosilicate glass tube: size: 3mm-320mm, and the tubes of 37, 47, 58, 70 for solar water heater. Usage:lighting, test tube Borosilicate glass ... tube 3.3 OD: 3mm~320mmColor: Clear / blue ... .3Feature: heat-resistant, anti-acid, anti-alkaliApplication: Lab glass ware, solar vacuum tube, lighting, handcrafts