Ductile fracture processes leading to failure in metallic materials involve different size scales depending on the prevailing stress state. The predominant size scale at low triaxial shearing stress states is typically much smaller than the one involved at higher triaxial axisymmetric stress states. As an example, consider cup-cone fracture, often observed in uniaxial tension tests of ductile metals. It initiates as a high triaxial flat dimple rupture in the centre of the specimens and then changes into a low triaxial shear failure by void-sheet formation when approaching the free surface. Fracture theories naturally introduce a size scale from a dimensional point of view, and there is a history of development of nonlocal porous plasticity model for ductile failure and fracture involving one length parameter. Recently, models have been proposed that incorporates two or more length parameters into the constitutive modelling framework, see [1] and [2], for the purpose of capturing failure process occurring at different length scales. Consider again the cup-cone fracture in a uniaxial tension test. This mode of failure will prevail as long as the linear dimension of the specimen is sufficiently larger than the length parameter associated with the high triaxial failure in the centre of the specimen. However, when the linear dimension becomes similar to the characteristic length of the fracture process it will affect the mode of failure. Here, the mode of failure of a set of uniaxial tensile tests with specimen diameter ranging from 10 mm down to less than 1 mm will be discussed and accompanied with simulations of a two-length parameter nonlocal GTN model, which is shown to be a discriminating test of such a model.