Clear Borosilicate Glass Rod3.3 High borosilicate glass (also known as hard glass), also known as "borosilicate glass 3.3" or pyrex glass rod because the linear thermal expansion coefficient is (3.3 0.1)×10-6/K. Colored Borosilicate Glass Rod Type: High Borosilicate Glass Application: Decorations, Cosmetics Size: 3.5-46mm Density: 2.23G/Cm 3.