Some of the listed balls might be sold as a urethane, but they are not true urethanes like the formulas 15/20 years ago. Balls like the Grenade, Natural, Natural Pearl, SuperNatural, Blue Hammer (remake), Polar Ice Hybrid, Karma, and U2 (remake) have some resine mixed in. The only true urethanes I know of are the Mixes from Storm and the Tank are the only 2 balls I know of on the market that are 100% true urethane. The visionary Ogre urethane was a true urethane ball but that is gone now I believe.