Most of the pet urns have lids at the tops that you can open whenever you wish. Some receptacles are semi-permanently sealed with the help of screws—generally, cremation centres hand over ashes to the pet owner in plastic bags. To put remains in a permanent urn, you do not have to take the ashes out of the bag. You can just set the bag inside the urn as it is. In this case, no sealing is required. However, if you wish just to put the ashes inside the urn without a plastic bag, you might have to seal it so that no loss happens if the urn accidentally falls or breaks.