Rust Resistant Aluminum door with Steel inner body insert for added security and strength. MAGNETIC LATCH to hold door securely closed. The RetroFit is an easy, snap in replacement mailbox door, ideal for brick or monument mailbox repair. Installs easy in less than 5 minutes. IMPORTANT NOTE REGARDING MEASURING YOUR MAILBOX AND SELECTING THE PROPER SIZE: The best way to determine the proper size to purchase is to measure the dimensions of the opening of the mailbox canister not the door itself. The mailbox door can be measured dimensionally in two different ways. You can measure the size of the door, or measure the size of the opening of the mailbox canister. In the case of the mailbox door, the actual dimensions of the door are larger than the canister opening to accompany the hinge at the bottom and to extend beyond the opening and close properly around the outside of the mailbox canister. As a result you will have two accurate ways to measure the product. This ASIN is for a standard T1 USPS Postmaster Approved mailbox. Measurements for this product are as detailed below: Method A: If you measure the canister, the opening will be 6.25 inches by 8.0 inches. Method B: If you measure the door, you will get dimensions of approximately 7.0 inches by 9.0 inches. Please see the attached images and watch the video below to see how to properly measure your mailbox and purchase the correct size This product is not compatible with plastic mailboxes.