Parasolid files (.x_t for text format and .x_b for binary format) are CAD (Computer-Aided Design) files used for storing 3D solid models. They are the native file format for the Parasolid geometric modeling kernel, a widely used kernel in various CAD, CAM (Computer-Aided Manufacturing), and CAE (Computer-Aided Engineering) software applications. Parasolid files contain precise geometric representations of 3D objects, including information about surfaces, solids, curves, and topology. They are known for their robustness and accuracy in representing complex shapes. The format supports a wide range of geometric entities, such as NURBS (Non-Uniform Rational B-Splines) surfaces, analytical surfaces, and solid primitives. Because Parasolid is a kernel, the files are often used for exchanging 3D model data between different CAD systems, ensuring that the geometric integrity of the model is maintained during the transfer. The binary format (.x_b) is generally smaller and faster to read/write than the text format (.x_t). Parasolid is developed and licensed by Siemens PLM Software.