A device for stretching a plastic ring which comprises pushing means (2) and aloading body (5) which are reciprocallyslidable across a plurality of ribs (4) solidly constrained to the pushingmeans (2), and a plurality of grooves (6) afforded onthe loading body (5). The loading body (5) exhibits a first substantiallyconical portion (7) exhibiting a base (7a), having an externaldiameter (D) and an apex (7b). The loading body (5) further comprises a secondportion (8), contiguous to the first conicalportion (7) and exhibiting a proximal end (8a) and a distal end (8b).
