The Z dimension refers to the position of the light beam transmitting through the cuvette. It is an important specification when working with small-volume samples.

Go Direct SpectroVis Plus: 8.5 mm
UV-VIS Spectrophotometer: 8.5 mm
Fluorescence/UV-VIS Spectrophotometer: 8.5 mm

SpectroVis Plus: 19 mm (discontinued in early 2017)