It's a rubber grommet. fit the Lense tightly and fit into a 1" hole in the fin. once i was happy with the camera alignment I epoxied the camera body to the fin inside.
Eventually I'll up load a video to my unDNR Chevys YouTube
Thanks, I got a cheep ebay fin. remolded it to point down a little bit in the back. Did a cast then made a new one out of fiber glass. took a few tries lol
Just did this to my 17 2500
Running a topper so I made a fiberglass shark fin to hold the camera. 3 layers of tint was hard to see out of. Bought a mirror with a cut coax cable. EZ fix for me. Ran my own coax to the fin and plugged it in...