What kind of balls did PBA bowlers use in the 90s?

[Ball99999]

Were they using reactive resins at the time? They seem to curve like urethane (like a smooth arc)

[J Anderson]

Some were using reactive resin, some were still using urethane. A lot of research has gone into both cover stocks and core design in the last 15-20 years. The early reactive balls had performance similar to low end balls of today.