The Brother D01LPB001 Ink Absorber Box is a printer maintenance part that collects residual ink during print-head cleaning. It is also described as a toner residual container, and its purpose is to receive the small amount of ink released in cleaning cycles.
Brother identifies the absorber box as a periodic maintenance item. It may need replacement as the printer performs ink-system purges and flushes; the number of these cleaning operations affects when replacement is needed.