Abstract: A pipe fitting having an improved means of securing a polymeric pipe thereto, wherein the first part of the pipe fitting comprises a head, a tail extending downstream of the head, an annular ridge surrounding the tail downstream of the head, and a male thread between the ridge and the head. A nut arranged to engage the first part of the pipe fitting, has a number of resilient spaced fingers extending upstream from an outwardly diverging mouth. The fingers have portions of a female movement which engage the male thread to resist upstream movement of the nut, but which can disengage and slide ("ratchet") over the male thread if the nut is moved in a downstream direction.