The model number is stamped on the side, top or bottom of the Andersen® insect screen frame. For example, 24310 is stamped on the insect screen as shown below. If you do not see the stamped model number, please search by the visible glass size.
From the interior of your window please measure the unobstructed glass you can touch on the lower sash, width by height.
Note: Do not guess your sizes always measure to ensure accuracy.