It's 12mm MDF but that is only on the side consoles; the rest of the build was connected to my main platform with is another 12mm MDF so most of the weight-bearing areas have 24mm MDF essentially. There are also areas after the MDF that have a good amount of timber, such as the rails areas of my setup. However, the issue is whether the MDF can take the weight and not compress or come apart even if the screws can go deep enough to hold the castor wheels in place.