The printer estimates the amount of waste ink and stores the count in a chip. The chip is mounted on the maintenance box. When a printer expects the box to be full, it will stop working until the box is replaced. Error messages like 'Epson ink pad is at the end of its service life', or 'parts inside the printer have reached the end of their service life' are some examples of such issue. This resetter is a hardware solution that makes the volume count back to zero.
The procedure is simple: take the maintenance box out and find the chip. Put the chip on this resetter and press down. Hold it for few seconds and the counter will be reset to zero. A hardware solution is not free. However, they are more reliable because they are made for a specific machine.