Clear vials offer maximum visibility. 15 x 45 mm, 1 dram (4 ml) clear borosilicate glass vial with 13-425 black phenolic rubber lined cap attached. Made of type i borosilicate glass, providing exceptional resistance to heat shock and chemical leaching. the glass is non-porous and has no catalytic affect. Because the boron oxide particles in the glass are so small, the silicate is held more closely together, resulting in a much stronger glass for your laboratory needs. Attached black phenolic caps with 14b white rubber liners are autoclavable. this liner is FDA approved for food and pharmaceutical applications. excellent properties of resilience, resistance to moisture vapor and relatively low gas transmission.