It has been long known that ultra-high molecular weight polyethylene (UHMWPE) can be gel-spun to yield high modulus and strength fibers, often above 100 GPa and 3 GPa, respectively. These properties, while impressive, still fall below their known theoretical maximum values. A recent study shows that ultra-drawn UHMWPE submicron fibers can exhibit an unparalleled combination of modulus, strength, and toughness. Such combination is believed to originate from a) high strain during the processing step and b) relatively defect-free nature of these materials below a critical dimension; the latter is known to follow Griffith's criterion. Herein reported is ultra-drawn high density polyethylene (HDPE) films with comparable mechanical properties that exhibit a range of thickness from 1 to 1000 microns. The findings from both UHMWPE fibers and HDPE films are compared to examine whether Griffith's criterion upholds for both cases.