Reactive resin balls, commonly known as reactive balls are used to revive in a rejuvenator. The other types of balls (plastic and urethane) are not porous like reactive balls. Thus, they do not soak up the oil from the lanes. The surfaces of the reactive balls have pores to give them a good grip on the lane. Due to recurrent uses, the pores get clogged up with oil and skids on the lane, failing to give the usual good grip over the lane. That is why reactive balls need to be revived.