You will find this information in the Specifications tab (toward the bottom of each product page). Minimum inside mount depth is the amount of depth required to securely mount the product inside the window opening. The minimum flush mount depth is the required mount depth needed to install the product and not have it extend outside of the window opening. If you have shallow depth, you would be able to install the product (as long as you have the minimum depth), but part of the item will protrude from the opening.