The HI731336N are the replacement caps that screw on the glass cuvettes used with the HI977xx series portable photometers. Each cap has a locking indexing tab that ensures the cuvette is inserted into the photometer in the same position. The caps are also used to block any light that would interfere with the optically based measurement. The HI731336N includes 4 caps.

• Locking index tab for proper alignment in the photometer
• Light blocking to prevent stray light from entering