I'm working now to replace all my Port Lights.
Mine are old cheap plastic ports that have worn out.
Some leak, some are cracked and crazed. All need replacing.
3 small ports in the front and 4 Large ports in the back, on both sides. 14 total.
I spoke with Ms.Teri in the NFM customer service dept and she walked me through the measuring dance. They have a video showing me how easy it is to install the new ones.... So, i ordered two sizes for samples to see how they fit. Next i took two days to remove the old ones. Note to self, there is a pretty large learning curve involved in the port process. (the install video shows how to install, not how to remove 30 year old cracked crappy ports with hard thick adhesive.)
I'm still learning. But i'm better today than yesterday.
My new ports will be arriving later this week. I'll post photos after the install.