This is a very great question. It is very important that all product descriptions are read carefully before making a final purchase. The tarp covers sold in our canopy replacement section are larger than the listed frame size to accommodate for the rise in peak. For example, the 10 x 20 frame replacement cover will come in a package that reads 12 x 20 on the package. Most canopy frames sold in major retail stores are of the high peak variety. This high angled roof must have more fabric to accommodate the pitch. However, not all manufacturers frames are the same. Obtaining a good measurement is the sure way to be certain the correct item is ordered. The three most important measurements are the width from inside leg to inside leg, the height from ground to center peak and the length of one side of the roof rafter. You can also measure the peak from one corner fitting, up and over the peak to the other corner fitting. This will tell you how much fabric is needed to cover the peak. Most canopy replacement tarps will have a measuring diagram to assist you in your decision. For further questions you can call us at (813) 442-7042.