An assembled preform (1) is provided for the making of a blown container, comprising a first external preform body (10) which comprises a neck part (2) which has an external region (4) which includes a threaded region (5) and an internal surface (3), and a second internal preform (11) which is suitable to be completely contained within said first external preform body (10), said second internal preform (11) having a neck region (12) suitable to cooperate with said neck internal surface (3) of said first external preform (10), the preform being characterized in that said neck region (12) of said second internal preform (11) comprises locking means (13,14) integrally obtained on the material of said second preform (11) and suitable for cooperating by blocked interference with said internal region (3) of the neck part (2) of said external preform (10) when said second internal preform (11) is inserted in said first external preform (10).

A preform (3) of a plastic container, comprising an outer preform (1) and an inner preform (2) inserted into the outer preform (1); wherein the outer preform (1) and the inner preform (2) are made of a mutually different material, in particular of a mutually different polymer; wherein the outer preform (1) is provided with at least one vertical protrusion (14) in contact with the inner preform (2); and wherein the outer preform (1) is made of a polar polymer and the inner preform (2) is made of an apolar polymer.

A method of producing containers with at least one enhanced property, such as high strength, sturdy, durable, and recyclable are described herein. The container so formed have ribs/patterns at the inner surface, leaving the entire outer surface for decorative or marketing purposes. The ribs/pattern is selected from linear lines, curved lines, honeycombs, hexagons, square, rectangular, circular and combination thereof. The containers so formed may have reduced amount of materials used.