X-Facto Pro.
I got one myself, not yet drilled.
I emailed Storm a few weeks ago and they sent me the following data.
It's basically X-Factor core and XXX-Factor coverstock.
PRO X Factorâ„¢ Technical Data
• Coverstock: Monsoon™ Pearl Reactive
• Factory Finish: 1500-grit Polish
• Weight Block: RAD™ Motion Control Technology
• Color: Purple / Blue / Silver Pearl
• Durometer: 73-75 Rex D-scale
• Radius of Gyration: 2.53 (Low)
• Differential: .058 (High)
• Mass Bias Differential: .013 (High)
• Flare Potential: High (6†plus)
• Logos – Storm, Flying ‘S’, PRO X Factor, ‘Eye of the Storm’ center of gravity, ‘RAD’ mass bias location
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The Angry Bowler