Wilson Staff Zip Zero Compression Core Golf Balls The unique rubber blend in the core uses a minimum of curatives to produce an ultra soft Patented HPF mantle layer encases the zero compression core with a speed generating mantle for distance and higher iron spin rate Super soft ionomer cover grabs the clubface for higher spin and amazingly soft feel The new 302 PhD aerodynamics feature unique flat bottomed Higher spin, longer distance, unmatched soft feel. Performance achieved Very low compression core with good resilience Shallow dimples rip through the air to create a more stable, penetrating ball flight