The most popular brand for sealing is DICOR. Works great, easy to use and quite durable. Easily repaired and a fraction of the cost of some others.
2003 Dodge HO 6 speed Laramie Dually, Jordan controller, RDS fuel tank, Air Ride 25K hitch
Carriage 36' fiver, Onan 6500, Prosine 2K inverter, 3 slides, MORyde IS and Kingpin