A cooling tube assembly for operating on a malleable molded plastic part. The cooling tube assembly comprising a porous tube/insert having a profiled inner conditioning surface, and a vacuum structure configured to cooperate with the porous tube. In use, the vacuum develops a reduced pressure adjacent the inner conditioning surface to cause an outer surface of the malleable molded plastic part, locatable within the cooling tube assembly, to contact the inner conditioning surface of the porous insert so as to allow a substantial portion of the outer surface of the malleable part, upon cooling, to attain a profile substantially corresponding to the profile of the inner conditioning surface. The cooling tube assembly having a simplified cooling structure that includes a cooling channel configured on the porous insert, the surface of which include a surface treatment for a sealing thereof to substantially avoid a leakage of coolant therethrough.