The ARB annex is the perfect way to add a little additional living space to your roof top tent. This additional zip on room will fit a couple of extra cots if you’d like to have the kids sleep downstairs or it also provides a terrific dressing room or concealed location to keep your waterless toilet. This part number will fit the following makes/models: The ARB Annex Can be Attached to Any Series III ARB Simpson Rooftop Tent