CAG is right.
Despite the roof being fiberglass, the sealant on the openings is a standard item and is used on all kinds of different types of roof material. Dicor self-leveling lap sealant is most common.
Check it frequently.
I intend to put Eternabond tape over all my seals, but I will still inspect 2x a year.
Fiberglass roof is not impenetrable, so you still need to be checking for damage even if you install a product that covers the seals.
-2018 Greyhawk 29MV
-2020 Jeep Wrangler Unlimited (JLU) (Primary Toad)
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-2014 Jay Flight 28BHBE & Ram 2500 6.4L CC 4x4 (sold)