These work great as long as you release the mice outside soon after they've been trapped. As other reviewers have said, the mice can pull the door up and escape. That happened at least twice when they were inside for more than a few minutes. The traps have 3 major design flaws. First, the door should not have vent holes, their tiny claws can pull the door up with those. Second, the spring on the door needs to be much stronger. Third, the door needs to be a fraction of an inch longer so there is not a tiny space beneath the door, they can also get their tiny claws in that space and pull the door up. If they would make these modifications, the traps would work perfectly.