If you need to perform automatic sampling, it is recommended to use a Cap with a center hole to facilitate automatic injection needles sampling.9mm Screw Top PP Cap for PERKINELMER9mm Blue Plastic Screw Caps is suitable for: 9mm Short Thread HPLC VialsCaps Material: polypropylene, size: 11.5*6mm, inner diameter: 9mm, with 6mm Centre Hole or