Only urethane. I tried a friend's ball with vinyl, and it was horrible for me. Much too slick, espcially when the thumb becomes wet from sweat in summer, and IMHO not easy to manipulate for adjustments.
Having urethane inserts in my balls was a real step forward, and I like to have them rather loose, but with a sanded/matte surface. I also tried a sheen/polished surface, but this caused the ball to fall off of my hand to early and me to grip it too tight.
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DizzyFugu - Reporting from Germany
Team X website & more about me
"Put some make-up on your face
Make this world a better place!"
Kahimi Karie, 'Good morning world'