A modifier for forming sub-ambient temperature use containers includes (a) from 20 wt % to 40 wt % of a block composite, the block composite including (i) an ethylene-propylene copolymer, (ii) an isotactic polypropylene polymer, and (iii) a block copolymer, (b) from 40 wt % to 60 wt % of a polyolefin copolymer, the polyolefin copolymer being derived from ethylene and at least one of a C3 to C10 alpha-olefin, having a melt index from 100 g/10 min to 1500 g/10 min, according to ASTM D1238 and at 190° C./2.16 kg, and having a density from 0.860 g/cm3 to 0.900 g/cm3, and (c) optionally, from 0 wt % to 30 wt % of at least one of a first additional copolymer that has a refractive index from 1.490 to 1.510 and a second additional copolymer that is miscible with polypropylene.