Craig,
I can't remember where I got mine but when I built my Cobra I had the same problem and I got some that was on a bulk roller at one of the Auto Supply houses around here. They had 3 sizes I believe it was and gave me a foot or so of each to bring home and try to see which size worked best. I then went back and just bought it by the foot. And it was hollow and rubber. I had to get glue to stick it on as it never had any sticky side, but I had it on there since 1996 and my Cousin tells me it is still just like new. I used it around the trunk lid and doors.
Ron
