The HP CZ999A is a booklet maker/finisher accessory that attaches to HP's M855 and M880-series LaserJet Enterprise printers, adding automated saddle-stitch booklet-making (folding and stapling multi-page documents into a booklet) plus 2- or 4-hole punching, at a rated capacity of up to 3,000 sheets. It's bought by print/reprographics departments and offices producing finished documents in-house - manuals, reports, programmes, training materials - that would otherwise need to be sent out for professional finishing. It only works as an add-on to compatible M855/M880 printers, not as a standalone device.