The DWK Wheaton Black Phenolic Screw Caps 15-425 with PTFE Insert provide a reliable and secure seal for laboratory samples. These high-quality black phenolic caps are designed with a white PTFE insert, offering excellent chemical resistance and ensuring a tight, leak-proof seal. The 15-425 size is compatible with standard laboratory vials, making these caps ideal for a wide range of applications, including chemical, pharmaceutical, and biological research. The pack of 200 caps is perfect for high-volume usage in laboratory environments.