2 mL Screw Top Vials & Screw Caps. Aijiren 2 mL screw top vials are constructed from from Type 1 borosilicate glass, with low metal content, to protect your sample from destabilizing or leaching. Our 2 mL screw glass vials are available in both amber and clear. The associated 9 mm screw caps and closures come with your choice of septa constructed from either PTFE silicone or natural red rubber.