PolyMag® screw caps are designed for automated applications and instruments using a magnetic sample transport system. This PolyMagnetic cap combines the tried and true functionality of a standard 18 mm screw cap with a built-in steel overlay design. This cap eliminates the need for hard to crimp steel caps yet still allows for transport with a magnetic sample transport system. The unique design of the cap does not alter the compatibility of glass or plastic 18 mm thread vials providing an excellent seal between the cap and vial. Available in 18 mm for Dynamic and Static Headspace techniques. The PolyMag screw cap is not designed for headspace applications where the vial oven temperature exceeds 130°C. Caps are lined with the SPME MicroCenter® liners along with a range of standard headspace silicone/PTFE liners.