An end closure device (2) adapted to be used in connection with internal hydrostatic pressure testing of polymer tubes and comprising a mainly dome-shaped end cap (4) provided with sealing means for establishing a pressure-proof connection with opposite end parts of a sample (6) of the tube to be tested, an exterior ring-shaped part (14) of said dome-shaped end cap (4) being adapted to be connected with at least one or more squeezing parts (10) adapted to be assembled around said opposite end parts of said sample (6) of said tube to be tested, where said one or more squeezing parts (10) each being built-up of a number of piled up and interconnected plate elements (16) the configuration of each of which being provided by a cutting operation such as laser cutting or water cutting. By the concept of the present invention it becomes possible to vary both the internal configuration and the thickness of the piled-up plate members forming at least the squeezing parts of the end closure device. In other words it would be possible to built-up squeezing parts with any possible internal configuration without using milling tool operations or machining at all.