This unit installs on the top of the printer. This unit supports up to 1,500 sheets of paper (20 lb, 75 gsm). Envelopes, card stock, transparencies and labels are also supported with this unit. When both an Output Expander and High Capacity Output Expander are installed, the Output Expander must be installed above the High Capacity Output Expander. The High Capacity Output Expander supports bin ‘full’ sensing.