We use a 19mm (3/4") thick back, and hold that back off the wall 10mm (3/8") to leave room for the hanging rail that is part of the suspension system we use to install Cabinotch Full Access wall cabinets (see the Suspension System question for more information), so the cabinet will have 1- 1/8" less interior depth than the total cabinet depth. To make certain the end user will have adequate interior space to store their dishes (over-sized plates have become very common place), we have bumped our default cabinet depth to 330 (13"). You are in full control of the wall cabinet depth, so you can set it to anything you want, but we wanted our default depth to accommodate as many over-sized dishes as possible. Of course there are some that would require a 458mm (18") deep cabinet, but a 330mm (13") depth should accommodate the vast majority of over-sized plates.