U-Form shape with strong walls made of borosilicate 100mm length and 12mm diameter 2mm bead 100 mm Absorption Tube, Calcium Chloride U-Form, borosilicate glass - Eisco Labs Eisco Labs Borosilicate glass has the following heat tolerances: Strain Point -515°C | Annealing Point 565°C | Softening Point 820°C.