The invention relates to a dart (10) comprising a body, the body defining a chamber (24) having a plunger located therein to operatively deliver a substance through a hypodermic needle (32) extending through a front end of the body, and a retainer comprising a barb body locatable on the hypodermic needle (32) characterised in that the barb body is threaded. The invention further relates to a dart retainer, wherein the retainer comprises of a threaded barb body locatable on a hypodermic needle (32) of a dart (10).