What is the inside of a white pool ball made out of?

The exacting requirements of the billiard ball are met today with balls cast from plastic materials that are strongly resistant to cracking and chipping. CurrentlySaluc, under the brand names Aramith and Brunswick Centennial, manufactures phenolic resin balls. Other plastics and resins such as polyester (under various trade names) and clear acrylic are also used, by competing companies such as Elephant Balls Ltd., Frenzy Sports.