Most of these are meant for more standard sized mattresses. You’ll find that the size options on them vary, but most commonly they’re at least be available in sizes Twin through King. If you’re searching for a liner for your crib’s mattress, you’ll want to narrow your search down to those terms specifically. If you like any of these fabrics and feels, you also can always order and cut down to size. Just be sure to secure it around the crib’s mattress so that Baby can’t pull it loose as that poses a choking hazard.