The dimensions of a cross pipe fitting depend on the size of the pipes that it is connecting. The dimensions can be expressed in various ways, including the outside diameter (OD), the inside diameter (ID), the wall thickness, and the center-to-end distance. The dimensions are typically specified in industry standards such as ASME B16.9 or ASTM A234. The dimensions can also vary depending on the material of the fitting, such as stainless steel, carbon steel, or PVC.