Method of forming a closure

A method of forming a bi-injected closure, comprising:

• forming an inner cap with a top plate and a depending cylindrical sidewall in a first injection moulding phase using a first mould part, the sidewall of the inner cap formed so as to include two external sealing support areas, the sealing support areas comprising radial steps which extend outwardly in a radial direction from the sidewall and which flank a portion of the sidewall onto which an outer ring is to be formed;
• changing the first mould part for a second mould part, and closing the second mould part onto the radial steps of the sealing support areas on the sidewall of the inner cap, such that the second mould part presses onto and seals against the two external sealing support areas so as to create a seal with the inner cap and delimit a cavity for the outer ring between the two external sealing support areas;
• and
• forming the outer ring around the sidewall of the inner cap whilst the second mould part is closed onto the sealing support areas in a second moulding phase, by injecting a material for the outer ring into the cavity for the outer ring.