The present invention relates to an ethylene/.alpha.-olefin interpolymer product comprising at least one .alpha.-olefin interpolymerized with ethylene and, characterized in at least one aspect, as having improved properties when utilized in a hot melt adhesive formulation. The invention also relates to a process for manufacturing the interpolymer product wherein the process comprises employing two or more single site catalyst systems in at least one reaction environment (or reactor) and wherein the at least two catalyst systems have (a) different comonomer incorporation capabilities or reactivities and/or (b) different termination kinetics, both when measured under the same polymerization conditions. The interpolymer products are useful, for example, in applications such as hot melt adhesives, and also for impact, bitumen and asphalt modification, adhesives, dispersions or latexes and fabricated articles such as, but not limited to, foams, films, sheet, moldings, thermoforms, profiles and fibers.