48PK Test Tubes, 7mL, 12x100mm - Rimmed - Light Wall, 1mm Thick - Borosilicate 3.3 Glass

This 48-pack contains heavy duty borosilicate 3.3 glass test tubes with a 7mL (0.2oz) capacity and uniform 1mm walls. Each tube measures 4 inches (100mm) tall with an outer diameter of 0.5 inches (12mm) and an inner diameter of 11mm. The tubes accept stoppers with a bottom diameter of 9 to 10mm and a top diameter of 13 to 15mm. 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. Uniform wall thickness prevents thermal stress concentrating at a thin point, which is the common failure mode over a burner. Borosilicate 3.3 glass withstands direct flame, high temperatures, and thermal shock, and the tubes are autoclavable for sterilization and reuse.