The Promax Plug Valve* was designed primarily to provide a solution for refilling Epson ink cartridges. Anybody who has tried to refill these later design single colour cartridges knows it is virtually impossible to achieve a successful result. That is until now!
All the later design Epson cartridges are spongeless in construction, which showed a departure from the previous conventional designs. In fact it would be fair to refer to them as the MkII Epson cartridge. So let’s do that from now on.
To be fair to Epson they make a good reliable product of high quality. They have also invested an enormous amount of money in R & D to invent new and better ways of producing high quality desktop printing to photographic standards. Their peizo-electric is a prime example. Without that there would be no dye sublimation printing as we know it. All this investment has to be protected, mainly by filing patents: - that’s what Intellectual Property rights are all about.
However, like all printer manufacturers they sell the printers cheap and the ink cartridges dearly. They probably lose money on the sale of a printer, but they sure make up for it on the replacement cartridge cost.