Here are two masu (wooden sake cups) from a Japan-Mori event. They are made of plastic, so I think they can be used outdoors. What do you think? I used them on the day of the event and then washed and stored them. They are not new, so please judge from the images. They have holes for attaching straps. Masu size: Approximately 6 x 6 x 4.2 cm Strap length: Approximately 104 cm