Aijiren Crimp Top Vials and Closures. Aijiren's 2 mL crimp top vials are constructed from Type 1 borosilicate glass, with low metal content, to protect your sample from destabilizing or leaching. Our associated crimp caps and closures come with a choice of etiher PTFE silicone, PTFE only, natural red rubber, butyl, or PTFE butyl materials.