For these printers:  Workforce Pro WF C5210, WF C5710, WF C5290, WF C5790, WF M5299.
 
The T6716 Ink Maintenance Box stores ink that gets flushed from the system during print head cleaning. Your printer and its software will let you know when the maintenance box needs to be replaced.

Note: Part T6716 is the same as T671600