I used Friskies: Oh No! Hairball, Helps Prevent & Eliminate Hairballs.
http://friskies.com/Cat-Food/More-Friskies/Oh-No-Hairball
I fed them 6 pieces per day per cat when they have the problems. After 8 bags, then 6 pieces per week. They both 15 lbs 2 years old adults.
Everyday dry food from Canadian superstore: Nutrition first premiere; Weight and hairball control.