The JT data format enables the creation and utilization of high-performance 3D models for all life stages of the product lifecycle. The compressible data format contains a CAD-neutral description of product data and acts as a key factor in the integration of multiple CAD and PDM systems. This Recommendation gives an overview about JT, the lightweight format for 3D data. After a short introduction a look in the brief history is given. Within the JT Workflow Forum project group, use cases for the application of JT in the context of virtual product engineering were specified. These are presented in this document.