The pin plug is required in port 6 of the Trap Valve pod assembly in the following configurations for the nanoACQUITY: Direct Injection, Single Pump Trapping, Vented Dual Pump Trapping, , and 2D with Dilution. To see the Fluidic Configurations for the nanoACQUITY UPLC, go to the Url Link below, under Systems select nanoACQUITY, click on the Waters Graphical Part Locator, and then choose Fluidic Configurations on the right side of the page. There will be the six different configurations of the nanoACQUITY that you can click on individually to see a larger image. There will also be a parts list for that specific configuration on the right side of the page.