3m makes the best marine/rv sealant. 5200 is the non removable / very difficult to remove kind. If you may want to remove it later use 4200. The regular 5200 takes 7 days to cure. If you need it to cure faster get the 5200 fast cure. I have used both and will be buying the fast cure exclusively in the future. It does the same thing and you don't have to wait 7 days.