24PK Test Tubes, 30mL, 20x150mm - Rimmed - Light Wall, 1.2mm Thick - Borosilicate 3.3 Glass

This 24-pack contains heavy duty borosilicate 3.3 glass test tubes with a 30mL (1oz) capacity and uniform 1.2mm walls. Each tube measures 5.9 inches (150mm) tall with an outer diameter of 0.8 inches (20mm) and an inner diameter of 18.8mm. The tubes accept stoppers with a bottom diameter of 15 to 16mm and a top diameter of 20 to 24mm. The rims are fire polished into a bead rather than cut. Fire polishing rounds the glass edge under heat and removes the microscopic flaws where cracking begins, producing a rim that resists chipping through repeated racking and washing and giving a stopper a defined seat. At 1.2mm the wall is matched to the larger diameters in this series so the tubes tolerate direct flame without a water bath. Borosilicate 3.3 glass withstands direct flame, high temperatures, and thermal shock, and the tubes are autoclavable for sterilization and reuse.