The X_B extension is given to files created with a CAD tool called Parasolid. X_B is a file containing a three-dimensional model made in the program. Files of this type are saved as binary.

The X_B format is used as a data exchange format between CAD modeling applications. These files replaced the older XMT_BIN and XMP_BIN formats . The text version of this type of model is the X_T file.