Disclosed herein is a composition substantially free of polyethylene, wherein the composition includes a thermoplastic material having certain specified mechanical properties, and about 2 wt. % to about 25 wt. % (based on the total weight of the composition) of an olefin mixture that consists essentially of a 30:70 to 70:30 weight ratio of a homogeneous ethylene-alpha olefin interpolymer and a propylene-based elastomer having at least 75 wt. % units derived from propylene and about 10 wt. % to about 25 wt. % units derived from a C2 or a C4-10 alpha olefin. The specified olefin mixture unexpectedly imparts to the overall composition mechanical properties (such as impact strength, for example) heretofore unattainable. These mechanical properties can be expected to be tailored to suit the end-use expected of the composition.