[Longhorn Man]

Many ppl just junk the cab once that happens, but they did just start selling this item a few years ago.
The sealant in the drip rail on top gets dry and shrinks over time, seems to be more of an issue on south and western trucks. Then, it rains and get wet inside there. Then, once it starts to rust a little, the rust holds the water when it rains again, and it evolves into a real seriouse issue. Personally, I would have to inspect the whole thing inbetween the inner and outer cab roof before I'd go replacing that panel... it would suck to replace it and then drop thousands in paint and body, only to discover that the surrounding area was already rusting, and only pops through AFTER you've spent your life savings.