Ready for use combination seals. No time consuming and tricky assembly. Caps and septa are pre-assembled to reduce contamination during sample preparation. Suitable for most chromatography applications. Available open top screw caps with 8-425, 9-425, 10-425, and 13-425 thread. Broad variety of different septa materials for most applications. Already pre-assembled seal with PRE slit/Bonded and standard septa available. Screw caps are pre-assembled for convenient use and are compatible with CTC PAL and Thermo TriPlus auto samplers. It comes with 1mm thick, Silicone/PTFE septa that can be inserted in these screw caps. Screw caps are used for GC or headspace analysis and are more reliable than magnetic crimp caps. These screw caps can be applied correctly to avoid errors in the data and to prevent from crimping and de-crimping of the hard metal that is used in the crimp cap.