This pack of 12 round-bottom test tubes is made from borosilicate 3.3 glass with a 50ml capacity per tube. Each test tube is fitted with a Bakelite screw cap and rubber liner to ensure a leak-proof seal, making them suitable for storing chemicals, samples, and biological materials. Each tube measures 5.9" tall and 1" wide (including cap). The borosilicate glass is autoclavable with superior chemical durability and a low temperature gradient, allowing the tubes to withstand high temperatures and thermal shocks.