Our extra large heavy duty 1/4” thick steel locking mailbox can hold up to the most severe abuse. The drop opening is 1-3/4” high by 11-1/2” wide mail slot which will allow large envelopes to easily drop into the locked secure receptacle. This high security mailbox is USPS approved and works as a High Security Payment Dropbox as well as a mailbox. This business mailbox with lock will work for both residential and commercial use. There are three lock options to keep your mail secure. The first lock option is a 7 pin tubular lock, the second lock is a high security Medeco lock and the third option is our most secure, the vault lock. The vault lock acts just like a vault so when the Medeco cam is turned to the locked position is also turns 2 large bolts which secure the door, much like a safe. There are two post options. The in ground post must be secured in the ground with cement and the surface mounted post has a flat plate on the bottom so it can be secured to most any hard level surface like a sidewalk or driveway. Pre drilled holes also allow you to secure to your existing post or hard surface. High Security Large Mailbox Specifications: Dimensions: 12″ Wide x 18″ High x 23″ Depth Drop slot opening: 11 -1/2″ wide x 1-3/4” high Outgoing compartment: 3″h x 5″d x 11 1/2″ w 1/4” thick steel body (3 gauge steel) 3/16” reinforced steel door 3 Lock options: Standard, Medeco, and Vault Lock Continuous welded steel hinge All hand welded design. (No spot welds or rivets) High performance powder coating w/ 2 Color choices: Black and Gray (custom colors available) Optional in ground or surface mounted post Made in the USA US POST MASTER APPROVED Due to the high security level this mailbox is at it is often purchased as a payment dropbox. The vinyl lettering allows for you to purchase vinyl lettering with your address number or we can apply "Payments" along the front in order to be used as a payment dropbox. The hole pattern for mounting is 4 holes which are 6 3/4" square and they are 1/2 inch holes.