Chromatography Sizes. Vials come in a variety of sizes to suit many needs. Standard sizes include 12x32mm (2mL), 15x45mm (4mL) and 8x40mm (1mL). Users may also choose vials with a normal (4 mm) mouth opening or wide (6 mm) mouth opening depending upon the cap type to be chosen. Important also is whether your sample is handled via Robotic Arm