This file is for a set of six sleepers, based on the older Peterbilt style. Each is 36", but three different heights. Why? The short ones are suitable for the older HO scale Ulrich Kenworth cab etc, the tallest for the latest generation of Ton (Tonkin) trucks. There are so many slight differences in cab sizing, I felt it best to offer a selection to suit. This file has passed the software checks, but if there's an issue, contact me via the shapeways link, or direct via email to modelmechanic@gmail.com