Free shipping on most products in the US & Canada. Patent Pending adapter matches the contour of the OEM roof so a standard RV style vent mounts to a flat surface. Prevents distorting the roof sheet metal or vent flange and can be used as an aid for locating the fan. The fan mounts to the outside adapter. Fan adapters work with the Maxxair Deluxe series and the Fan-tastic Vent fans. DIYvan is there for every step of our Do It Yourself Van Conversion with experienced advice and our full Impact Products line including 3M Thinsulate, 80/20 cross bars, solar mounting brackets, storage solutions and roof vent adapters.