Light-path length is the distant between the interior polished walls of a cuvette.
Light-path width is the distant between the interior un-polished walls of a cuvette.
Light-paths are measured in millimeters and can vary from 0.5 mm up to 200 mm. The most common light-path in use today is 10 mm. Most manufacturers provide a standard 10 mm rectangular cuvette holder with their machines, however this should be confirmed with the manufacturer because not all machines may be able to support a 10 mm holder.

Light-Path length and width