I was replacing an existing door knocker and was frustrated at the lack of detailed information available for these products in most cases. In other cases there was conflicting information about dimensions, size, etc. I was simply trying to match the general design and exact spacing of the existing mounting screw holes in my door, but with so little product information available it came down to trial and error. To help others that are in the same situation, I've documented the details of this product below and in some photos.This door knocker is not quite as thick as the one that I was replacing, but it was still fairly heavy and feels solid. The finish was clean and as described. The included hardware was adjustable to fit a variety of door thicknesses. The one I received was made in Taiwan. Of note, it came in a plastic-welded clamshell package, which had sharp edges and required a utility knife or scissors to open.Other note: I was replacing a custom engraved door knocker of a similar design which came from "Things Remembered" several years ago. They have since changed their unbranded stock model, so the only information I had to go on for the old knocker was that it was made in Spain. This item turned out to be an exact replacement in terms of overall design, finish, length, and width. It is a perfect fit for anyone replacing one of the old "Things Remembered" unbranded door knockers. I would buy this product again.Technical Information:The vertical spacing between the mounting screws is exactly 4.25 inches on-center.The hardware kit included 2 screws, two screw extensions, and two trim rings for the screws. The screws and the extensions both thread directly into the door knocker, so you can use the mounting screws without the extensions if your door is thin enough.The screws by themselves are 1.25" long. When the screw is threaded all the way in to the extension, the combination of the extension and screw together has an overall length of 1.75" (minimum). When the screw is all the way out of the extension (only inserted two complete turns), the overall length is 2.5" (maximum).I would estimate that this hardware configuration will support doors from about 1" thick up to about 2.25" thick.Installation Notes:1. When installing this door knocker, ensure that your holes through the door are perfectly level and straight. If not, the holes won't line up for the screws to meet up with the knocker. This is more critical when using the standoffs, since the screw and standoff must meet somewhere in the middle of the hole and there is no play/wiggle room. The person who installed the previous knocker I was replacing didn't do this, so I had a difficult time reaming out the existing holes in the door to line up properly.2. The instructions on the back are inaccurate or incomplete in places. Specifically:A. The instructions call for a 3/16" drill bit. If you only use the screws and not the extensions, this is fine. However if you use the extensions, a 1/4" bit is required. The extensions will not fit through the 3/16" hole.B. The instructions indicate that it can be used on doors up to 2-1/8" thick. Although not ideal, I would say you can probably go up to 2-1/4" thick. Because of the difference between the screw length and the minimum combined screw + extension length, there is a dead zone for door thicknesses between about 1-1/8" and 1-1/2" where the screw is too short by itself, but with the extension is too long.TIP: The instructions state that you can cut the screw to a shorter length, which will allow you to adjust for the dead zone or even use a door thinner than 1" if necessary. If you choose to do this, I strongly recommend threading a nut all the way down on the screw, then carefully cutting the screw down to length, and then removing the nut. Invariably cutting a screw damages the threads at the end and tends to keep it from threading in properly. By removing the previously placed nut after cutting, it straightens the threads back out at the tip of the screw and allows it to be easily threaded into the intended hole. Unfortunately I did not have an opportunity to determine the diameter and thread pitch for the included screws.I hope these details help you in determining if this product will fit your application.