All bags larger than 12″ x 12″ x 6″ will no longer be allowed in theaters under the new policy, which starts today. An exception will be made for bags used to carry medical equipment and diaper bags for customers with small children. Theaters will not provide a bag check for those who do bring larger bags and will instead require those guests to stow their bag elsewhere before entering the theater. Even small bags are also subject to search.

According to Cinemark, the ban is less about smuggling in a contraband bag of chips and more about safety. In 2012, a Cinemark theater in Aurora, Colo. was the site of a mass shooting where 12 people were killed and dozens were wounded.

Cinemark has 533 theaters in the United States.