In Japan, it is commonplace for a family to own a mailbox with a small mail slot. It is not able to accept a large mail, and approximately 65% of them are re-delivered later. This is waste of money and time. However, this Qual can realize to keep various sized mails. That is to say, this would possibly change our lifestyle and distribution system. Qual has a simple form and it is distinguished by a big dial. This is the result which we have sought the way how easy they could open and lock it for all the people.