(CNN) - Half of car booster seats don't fit all safety seat belts, according to the Insurance Institute for Highway Safety (IIHS).
The IIHS examined more than 80 booster seats in a new study.
Forty-one of them fell into the "check fit" category, meaning they didn't properly fit seat belts in every vehicle.
Six booster models were so bad that IIHS recommended parents avoid them.
The good news: Booster seats are getting better.
A record 31 boosters have been designated "best bets" or "good bets" by the IIHS.