END CAP

To obtain an end cap that enables a brazing material ring to be appropriately placed and brazing to be reliably performed when inserting and placing an insertion part of the end cap in an end part of a rail body and securing the end cap by brazing it with the brazing material ring and, also, that is unlikely to result in a broken rail body when internal pressure is applied. An end cap to be inserted into and placed inside an end part of a rail body and secured to an inner circumference of the rail body by brazing, wherein an outer circumference of an insertion part for insertion into the rail body comprises an engagement groove that is composed of a pair of side surfaces and a bottom surface and that is capable of engagement with a brazing material ring