Just some more Bowling Balls to add to the already abundant collection.
I shaded the inner finger holes with a 1) Black Material and 2) a Tan Material while in Edit Mode - Add Material - Assign, thus my Bowling Balls have 3 Slots for materials.
The first is rendered in Eevee and the main material uses a Voronoi Texture into a ColourRamp.
The second is rendered in Cycles and the main material uses a Wave Texture into a ColourRamp.