Golf balls comprising thermoplastic, thermoset, castable, or millable elastomer compositions are presently disclosed. The compositions comprise at least one regioselective polyisocyanate having an asymmetric structure and comprising at least a first NCO group and a second NCO group, the first NCO group being substantially more sterically interfered than the second NCO group. The first NCO group is directly attached to a tertiary carbon atom or is one methine carbon atom away from either at least one quaternary carbon atom or at least two tertiary carbon atoms. These elastomer compositions can be used in any one or more portions of the golf balls, such as inner center, core, inner core layer, intermediate core layer, outer core layer, intermediate layer, cover, inner cover layer, intermediate cover layer, and/or outer cover layer.