The results of this study indicate

The results of this study indicate that the nutritional hairball
preventative chew helps reduce the frequency of the clinical
signs of hairballs when fed daily to cats prone to hairballs.
Because the clinical effects of hairballs can be a chronic
problem in some cats, a more extensive trial monitoring cats for
a longer period would help determine if the hairball preventative chew is more effective when given as a long-term
prophylactic against the clinical signs of hairballs.