A dispenser assembly for dispensing a substance from a receptacle is provided. Preferably the collar therefore comprises outwardly projecting and elongated angled ribs for forming complementary elongated grooves in the outer surface of the ferrule. A method of assembling such a dispenser assembly upon a receptacle is also provided and comprises the important step of allowing the collar to rotate over the outer surface of the ferrule and towards the receptacle, such that the elongated ribs form complementary elongated grooves in the outer surface of the ferrule thereby forming an airtight seal between the dispensing assembly and the receptacle.