The clear bowling balls look magnificent and unique, as their outer cover is made up of transparent plastic, and can be fabricated using different means. One way is to paint its inner sides so as to look like a specific object. Most commonly used ones are skulls, professional logos, can be made to look like other sports balls like the basketball or the tennis ball, or may even contain funny designs or superheroes if they are meant for the kids or beginners. These inner painted balls have no cores, so they are not suitable for spinning the ball.
Cores play an important role in any ten pins game. The balls are made so that it has a core, which is either deformed on a side, or not in the centre making its centre of mass destabilized. This creates an imbalance, thus making the cores make each ball roll and move, as they tend to turn in that directions trying to stabilize its core, making it spin. As normal clear bowling balls have no core, a different version of them actually keeps the object inside, this behaves like the core. And the different shaped object used inside allows each ball to behave differently.
If you are a professional bowler, you should choose the balls with a core rather than the ones that are inner painted, which are mainly used to let others see how interesting it looks. Those balls use different shapes on cores, which can be cylindrical or cubical, and needs to be personalized with a particular design, as all designs don’t look equally good on a specific core shape. So choosing the core and designs are most important.