Paper Saver 664 ink is compatible with printers that use Epson 664 ink.  The ink comes in a bottle for filling the ink tank in the printer.  You should start using Paper Saver ink with a new printer that has clean, empty ink tanks.  If you put Paper Saver ink in printer that had regular ink in it before, the old ink will contaminate the Paper Saver ink so that it is no longer self-erasing.  The mixture of inks will typically clog the nozzles in the printer and make it unusable.

The Epson L121 and L120 printers are compatible and is available on eBay from Taiwan with fast shipping.