Generally speaking, a banner that is rated for indoor use can be used for outdoor installation as well. The main difference between indoor banners and outdoor banners is in the construction and finishing options you have to think of when you place the order. The outdoor banner is meant for outdoor installation, which means that they are exposed depending on the region to high winds. If exposed to high winds you might have to add reinforced corners, wind slits, hems, and other options that we offer for outdoor banners, also you would consider printing them on 15oz thicker material. With indoor banners, they are meant for indoor usage and they are not exposed to winds, heavy rain, or other type of precipitation as are the outdoor banners. You would not need wind slits or another type of finishing you might need for the outdoor banners. You might consider doing hems for the indoor material, just to add and extra safety if the size is big and it has to be hung for a long period of time.