An electrofusion fiting (20) comprises a fitting body (24) and an electrofusion collar (26). The fitting body (24) has an exterior surface (30), an interior surface (32), and a terminal portion (44) extending to a rim (34). The collar (26) has: an inner wall (42) having a heating element (60); a segmented outer wall (40) spaced radially apart from the inner wall; and a linking portion (46) linking the outer wall and inner wall. The fitting body terminal portion is between the inner wall and the outer wall. The collar and fitting body have interfitting features (150, 152) axially retaining the collar against extraction from the fitting body while permitting relative rotation of the collar and the fitting body.