Socket weld and butt weld fittings are governed by different applicable standards (socket weld fittings are ASME B16.11 and butt weld fittings are ASME B16.9), as there are differences between the two types of weld. Socket welds involve the insertion of the pipe into a recess at the joint and there is no need to bevel the pipe ends or prepare the materials other than to ensure they are clean. Butt welds require the fittings to be the same thickness as the pipes so that they can be welded. Butt welded joints also need to be bevelled at the ends. In addition to these practical differences, there are differences in performance, with butt weld fittings tending to be stronger. For this reason, socket weld fittings tend to be reserved for pipes with relatively small diameters. This difference in strength also means that butt welds are preferred for high temperature and pressure applications or where the weld joint strength does not have to be more than the base metal.