This converter is equipped with a built-in TTL PCB that connects a Nikon digital SLR with SEA&SEA Series-YS strobes and uses the cameras TTL flash adjustment to control the amount of light put out by the strobe. The converter allows quick switching underwater between TTL mode and manual mode from outside the camera. You can use the TTL correction dial after checking the results of a shot in the LCD monitor to adjust the amount of strobe light for the next shot. Because the converter comes with two separate strobe connectors, you can use advanced automatic TTL flash adjustment with two strobes.