Dresser Style 31 Line Caps are used to close off sections of a pipeline during construction and testing, and to cap off dead-ends in the line for future branch connections. Style 31 Line Caps are made from Style 38 Dresser coupling parts with a convex steel dished head welded into one end of the middle ring. One follower ring is welded to the cap itself, and only one gasket is required. The Style 31 is regularly supplied with a 1" NPT vent and plug off-center. When ordering, please specify whether vent is to be provided.