At one time, rice was used at currency. During this time masu was originally used as a measuring cup for rice. Today masu are used as vessels for sake. They are considered lucky, therfore are often used during important occasions. 
 
There are two ways to enjoy cold sake in a Masu; one is to pour sake directly into the Masu and the other is to put a glass inside the Masu. Whichver way you choose to enjoy your sake, we hope you enjoy the experience with Moon Bloom. Thank you for your purchase.