https://www.lockingsecuritymailbox.com/through-the-wall-letter-drop-slot-with-chute/ USPS mail chute slot for mail or payments. Adjustable from 5 to 12 inch walls. Made in the USA. Letter Drop Slot Features: Allows easy insertion of standard-sized letter envelopes and small packages Constructed of heavy duty steel Optional adjustable chute extension for up to 12 thick wall Anti-Phishing teeth helps prevent mail theft Letter Drop Slot Specifications: Drop opening: 10-5/8 wide by 2-3/4 high Rough opening 11.5 wide and 4 high Cover plate face is 14 wide X 6 H Door size: 4H x 11-3/4W Chute size is 11-1/2 wide X 4 high The optional chute extension slides over the fixed chute. For installation simply pre-drill holes into the side of the chute and secure to studs or masonry to desired length. You can apply a bead of adhesive caulking to the back of the cover plate to help secure and seal it into place.
Through the Wall Letter Drop Slot with Chute