13mm Screw Neck Closures are made of high-quality polypropylene. The thread shape inside the Cap can fit the automatic sample injection via very well, and it is also compatible with the automatic sampler. The 13mm Screw Neck Closures pre-assembled septum can reduce the chance of contamination during sample preparation and save time in laboratory sample preparation. Aijiren provides septa and slit septa. The normal available cap color is black, but other special colors can also be produced.