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 Machine (R.A.M.). These vials must use a nonstandard 9 mm vial cap size.