PTFE/silicone septa are most commonly used in HPLC applications, and pre-cut septa are easier to pierce with a needle. The cap color is generally black, but other special colors can also be produced accordingly. Easy to apply and easy to remove. Pre-installed caps and septa are very convenient. Aijiren 13mm Screw Closures are commonly used in 4ml Screw Top HPLC Vial. Aijiren can recommend the most suitable Closures for your HPLC Vial.