The HP Smart Tank Plus 651 Wireless All-in-One is a bulk-ink printer that produces quality output and costs little to use over time but lacks many of the convenient features of similarly priced competitors. Rather than using ink cartridges – which is common even on the best all-in-one printers – you buy the four inks by the bottle and pour each ink into the corresponding high-capacity tank. Instead of relying on printer cartridges to produce a print, ink tank printers use a refillable tank system and ink bottles to handle printing duties. Similar to filling up your gas tank, when your printer’s ink levels are running low, you need to fill the tank with the appropriate amount of ink from the bottle.