Does it have to be an Arctic Tern Overland window or door? Of course not. Many door and window manufacturer's products are compatible with the 2.5" Globe Trekker engineered panels. We've just done the research, and a very good window with great service, parts availability, and lead times ...at a great price, is Tern Overland windows and doors. We did the research so you don't have to. But if you want another brand, that's okay with us.