With a window sealing kit, you can get the most out of your air conditioner. You can use it to close off your window completely. This way, cold air can't escape, and hot air can't get in. Make sure you choose the right windows sealing kit for your window. You can find window sealing kits for side-hung windows, top-hung windows, sliding windows, windows that turn inwards and outwards, and even kits for your mailbox.