100PK Test Tubes, 25mL, 18x150mm - Rimmed - Light Wall, 1.2mm Thick - Borosilicate 3.3 Glass

This 100-pack contains heavy duty borosilicate 3.3 glass test tubes with a 25mL (0.85oz) capacity and uniform 1.2mm walls. Each tube measures 5.9 inches (150mm) tall with an outer diameter of 0.7 inches (18mm) and an inner diameter of 16.8mm. The tubes accept stoppers with a bottom diameter of 13 to 15mm and a top diameter of 18 to 20mm. At 18mm outer diameter these tubes fit the rack spacing used across most standard sets. The rims are fire polished into a bead rather than cut, which rounds the glass edge under heat and removes the microscopic flaws where cracking begins. The resulting rim resists chipping through repeated racking and washing and gives a stopper a defined seat. Uniform wall thickness prevents thermal stress concentrating at a thin point. Borosilicate 3.3 glass withstands direct flame, high temperatures, and thermal shock, and the tubes are autoclavable for sterilization and reuse.